JP2000294810A - Photo conductor - Google Patents
Photo conductorInfo
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- JP2000294810A JP2000294810A JP11099443A JP9944399A JP2000294810A JP 2000294810 A JP2000294810 A JP 2000294810A JP 11099443 A JP11099443 A JP 11099443A JP 9944399 A JP9944399 A JP 9944399A JP 2000294810 A JP2000294810 A JP 2000294810A
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- thin film
- semiconductor thin
- electrode
- light
- film layer
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Abstract
(57)【要約】
【課題】 本発明は、フォトコンダクタ（Photoconduct
or）に関し、特に高感度化と高速応答化とを実現したＭ
ＳＭ（Metal-Semiconductor-Metal）フォトコンダクタ
を提供する。
【解決手段】 ＭＳＭフォトコンダクタは、半導体基板
１０と、半導体基板１０の上に所定の波長の光が照射さ
れた場合に導電率が増加する光伝導半導体薄膜層２０
と、光伝導半導体薄膜層２０の上に形成されて互いに所
定の間隔を隔てて近接し、かつ、前記光を透過させる第
一及び第二の電極用半導体薄膜層３０、３１とを備え
る。
(57) [Summary] [PROBLEMS] The present invention relates to a photoconductor.
or), in particular, M which realized high sensitivity and high speed response
Provide SM (Metal-Semiconductor-Metal) photoconductor. An MSM photoconductor includes a semiconductor substrate (10) and a photoconductive semiconductor thin film layer (20) whose conductivity increases when light of a predetermined wavelength is irradiated onto the semiconductor substrate (10).
And first and second electrode semiconductor thin film layers 30 and 31 that are formed on the photoconductive semiconductor thin film layer 20 and are close to each other at a predetermined interval and that transmit the light.
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、フォトコンダクタ
（Photo conductor）に関し、特に高感度化と高速応答
化とを実現したＭＳＭ（Metal-Semiconductor-Metal）
フォトコンダクタに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductor, and more particularly, to an MSM (Metal-Semiconductor-Metal) realizing high sensitivity and high speed response.
It relates to a photoconductor.
【０００２】[0002]
【従来の技術】高抵抗半導体を用いたフォトコンダクタ
の一つであるＭＳＭフォトコンダクタは、その低容量
性、及び、光伝導効果（Photo conductive effect）に
よる数百ＧＨｚの高速応答性に特徴を有する。そのた
め、近年、ＭＳＭフォトコンダクタは超高速光半導体デ
バイスとして注目を集めている。2. Description of the Related Art The MSM photoconductor, which is one of photoconductors using a high-resistance semiconductor, is characterized by its low capacitance and high-speed response of several hundred GHz due to a photoconductive effect. . Therefore, in recent years, MSM photoconductors have attracted attention as ultra-high-speed optical semiconductor devices.
【０００３】図１は、従来のフォトコンダクタの断面図
である。フォトコンダクタの一つである従来のＭＳＭフ
ォトコンダクタは、半導体基板１０と光伝導半導体薄膜
層２０と第一及び第二の電極５０、５１とを備える。半
導体基板１０は、半絶縁性半導体材料で形成される。光
伝導半導体薄膜層２０は、高抵抗半導体材料を用いて半
導体基板１０の表面に成長させる。第一及び第二の電極
５０、５１は、金属を薄膜状にして光伝導半導体薄膜層
２０の上にそれぞれ蒸着し、所定の間隔を隔てて互いに
近接させる。FIG. 1 is a cross-sectional view of a conventional photoconductor. A conventional MSM photoconductor, which is one of the photoconductors, includes a semiconductor substrate 10, a photoconductive semiconductor thin film layer 20, and first and second electrodes 50 and 51. The semiconductor substrate 10 is formed of a semi-insulating semiconductor material. The photoconductive semiconductor thin film layer 20 is grown on the surface of the semiconductor substrate 10 using a high-resistance semiconductor material. The first and second electrodes 50 and 51 are formed by depositing metal on the photoconductive semiconductor thin film layer 20 in the form of a thin film, and are brought close to each other at a predetermined interval.
【０００４】第一及び第二の電極５０、５１の間を通過
させて光を光伝導半導体薄膜層２０に照射すると、光伝
導半導体薄膜層２０において光励起により自由キャリア
が生じる。自由キャリアが生じると光伝導半導体薄膜層
２０の抵抗は低下し、第一及び第二の電極５０、５１に
電圧を加えると光伝導半導体薄膜層２０を介して電流が
流れる（光伝導効果）。When light is applied to the photoconductive semiconductor thin film layer 20 by passing between the first and second electrodes 50 and 51, free carriers are generated in the photoconductive semiconductor thin film layer 20 by photoexcitation. When free carriers are generated, the resistance of the photoconductive semiconductor thin film layer 20 decreases. When a voltage is applied to the first and second electrodes 50 and 51, a current flows through the photoconductive semiconductor thin film layer 20 (photoconductive effect).
【０００５】図２は、従来のフォトコンダクタの平面図
である。第一及び第二の電極５０、５１はぞれぞれ互い
に近接する電極近接部５２ａ、５２ｂを有する。電極近
接部５２ａ、５２ｂの構造としては櫛型構造が用いられ
る。櫛型構造が用いられるのは、電極同士を広い幅にわ
たり近接させて電界を多く生じさせるためであり、ま
た、光伝導半導体薄膜層２０の受光量を多くするためで
ある。照射光は、電極近接部５２ａ、５２ｂを全て覆う
ように照射される。電極近接部５２ａ、５２ｂは、対向
方向へ延びる複数の突片をそれぞれ有する。FIG. 2 is a plan view of a conventional photoconductor. The first and second electrodes 50 and 51 have electrode proximity portions 52a and 52b which are close to each other. A comb structure is used as the structure of the electrode proximity parts 52a and 52b. The comb structure is used in order to generate a large electric field by bringing the electrodes close to each other over a wide width and to increase the amount of light received by the photoconductive semiconductor thin film layer 20. The irradiation light is applied so as to cover all the electrode proximity portions 52a and 52b. The electrode proximity portions 52a and 52b each have a plurality of protruding pieces extending in the facing direction.
【０００６】電極近接部５２ａ、５２ｂに照射される光
のうち光伝導半導体薄膜層２０へ入力される割合をＳ、
電極近接部５２ａ、５２ｂの間隔をＬ、電極近接部５２
ａ、５２ｂの各突片の幅をＷとすると、 Ｓ＝Ｌ／（Ｗ＋Ｌ） ・・・式（１） となる。ＷをＬよりも十分に小さくすればＳが大きくな
る。ＭＳＭフォトコンダクタの導電性を高めるには電極
近接部５２ａ、５２ｂの間隔Ｌを小さくする。ＭＳＭフ
ォトコンダクタの受光量を高めるには照射光の入力割合
Ｓを大きくする。しかし、間隔Ｌを小さくしつつ、同時
に入力割合Ｓを大きくすることは困難である。[0006] The ratio of light input to the photoconductive semiconductor thin film layer 20 of the light irradiated to the electrode proximity portions 52a and 52b is represented by S,
The distance between the electrode proximity portions 52a and 52b is L, and the electrode proximity portion 52
Assuming that the width of each of the protruding pieces a and 52b is W, S = L / (W + L) (1) If W is made sufficiently smaller than L, S will increase. To increase the conductivity of the MSM photoconductor, the distance L between the electrode adjacent parts 52a and 52b is reduced. To increase the amount of light received by the MSM photoconductor, the input ratio S of irradiation light is increased. However, it is difficult to increase the input ratio S while reducing the interval L.
【０００７】[0007]
【発明が解決しようとする課題】光伝導半導体薄膜層２
０として用いる半導体材料の中には、電極に用いる金属
にオーミック接合させることが困難な材料がある。例え
ば、InGaAs（インジウム・ガリウム・砒素）等の半導体
を光伝導半導体薄膜層２０に用いる場合、第一及び第二
の電極５０、５１との接合界面に電位障壁（ショットキ
ー障壁）が生じてしまう。ショットキー電極を形成した
場合、接触容量によりＭＳＭフォトコンダクタの高速応
答特性が阻害されるという欠点があった。SUMMARY OF THE INVENTION Photoconductive semiconductor thin film layer 2
Among the semiconductor materials used as 0, there are materials that are difficult to form an ohmic junction with a metal used for an electrode. For example, when a semiconductor such as InGaAs (indium gallium arsenide) is used for the photoconductive semiconductor thin film layer 20, a potential barrier (Schottky barrier) occurs at the junction interface with the first and second electrodes 50 and 51. . When the Schottky electrode is formed, there is a disadvantage that the high-speed response characteristic of the MSM photoconductor is hindered by the contact capacitance.
【０００８】また、従来のＭＳＭフォトコンダクタの受
光量を高めるためには照射光の入力割合Ｓを大きくする
のが望ましいが、電極近接部５２ａ、５２ｂの各突片の
幅Ｗと間隔Ｌとを同時に小さくするのは困難であった。In order to increase the amount of light received by the conventional MSM photoconductor, it is desirable to increase the input ratio S of the irradiation light. However, the width W and the interval L of each protruding piece of the electrode proximity portions 52a and 52b are required. It was difficult to make them smaller at the same time.
【０００９】そこで本発明は、上記の課題を解決するこ
とのできるフォトコンダクタを提供することを目的とす
る。この目的は特許請求の範囲における独立項に記載の
特徴の組み合わせにより達成される。また従属項は本発
明のさらなる有利な具体例を規定する。Accordingly, an object of the present invention is to provide a photoconductor which can solve the above-mentioned problems. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous embodiments of the present invention.
【００１０】[0010]
【課題を解決するための手段】上記課題を解決するため
に、本発明の第１の形態においては、光が照射されるこ
とにより導電率が増加するフォトコンダクタであって、
所定の波長の光が照射された場合に導電率が増加する光
伝導半導体薄膜層と、前記光伝導半導体薄膜層の上に形
成され、所定の間隔を隔てて互いに近接する第一及び第
二の電極用半導体薄膜層と、前記第一及び第二の電極用
半導体薄膜層の上にそれぞれ形成された第一及び第二の
電極とを備える。According to a first aspect of the present invention, there is provided a photoconductor whose conductivity is increased by being irradiated with light,
A photoconductive semiconductor thin film layer whose conductivity increases when irradiated with light of a predetermined wavelength, and a first and a second formed on the photoconductive semiconductor thin film layer and adjacent to each other at a predetermined interval. An electrode semiconductor thin film layer, and first and second electrodes respectively formed on the first and second electrode semiconductor thin film layers are provided.
【００１１】本発明の他の形態においては、前記第一及
び第二の電極用半導体薄膜層の導電率は、前記光が照射
された場合の前記光伝導半導体薄膜層の導電率より高
く、前記第一及び第二の電極用半導体薄膜層は、それぞ
れ前記第一及び第二の電極にオーミック接合する。In another aspect of the present invention, the conductivity of the first and second electrode semiconductor thin film layers is higher than the conductivity of the photoconductive semiconductor thin film layer when irradiated with the light. The first and second electrode semiconductor thin film layers are in ohmic contact with the first and second electrodes, respectively.
【００１２】本発明のさらに他の形態においては、前記
光伝導半導体薄膜層がInGaAsで生成され、前記第一及び
第二の電極用半導体薄膜層がInPで生成され、前記第一
及び第二の電極が、前記第一及び第二の電極用半導体薄
膜層に接合するAuGe層と、前記AuGe層の上に形成される
Au層とを有する。In still another embodiment of the present invention, the photoconductive semiconductor thin film layer is formed of InGaAs, the first and second electrode semiconductor thin film layers are formed of InP, and the first and second electrode semiconductor thin film layers are formed of InP. An electrode is formed on the AuGe layer, which is bonded to the first and second electrode semiconductor thin film layers, and the AuGe layer.
Au layer.
【００１３】本発明のさらに他の形態においては、前記
第一及び第二の電極用半導体薄膜層が、前記第一及び第
二の電極用半導体薄膜層の断面幅よりも広い幅にわたっ
て互いに近接する近接部をそれぞれ有する。In still another embodiment of the present invention, the first and second electrode semiconductor thin film layers are close to each other over a width larger than a cross-sectional width of the first and second electrode semiconductor thin film layers. Each has a proximity portion.
【００１４】本発明のさらに他の形態においては、光が
照射されることにより導電率が増加するフォトコンダク
タであって、所定の波長の光が照射された場合に導電率
が増加する光伝導半導体薄膜層と、前記光伝導半導体薄
膜層の上に形成され、所定の間隔を隔てて互いに近接
し、かつ、前記光を透過させる導体又は半導体で生成さ
れた第一及び第二の電極層とを備える。According to still another aspect of the present invention, there is provided a photoconductor whose conductivity is increased by light irradiation, wherein the photoconductive semiconductor increases in conductivity when irradiated with light of a predetermined wavelength. A thin film layer and first and second electrode layers formed on the photoconductive semiconductor thin film layer, which are close to each other at a predetermined interval, and which are formed of a conductor or a semiconductor that transmits the light. Prepare.
【００１５】本発明のさらに他の形態においては、前記
第一及び第二の電極層が、半導体で生成された半導体薄
膜層であり、前記第一及び第二の電極層が半導体で生成
された半導体薄膜層であり、前記第一及び第二の電極層
を形成する半導体薄膜層の光吸収端波長が、前記光伝導
半導体薄膜層の光吸収端波長より短い。In still another aspect of the present invention, the first and second electrode layers are semiconductor thin film layers made of a semiconductor, and the first and second electrode layers are made of a semiconductor. The light absorption edge wavelength of the semiconductor thin film layer forming the first and second electrode layers is shorter than the light absorption edge wavelength of the photoconductive semiconductor thin film layer.
【００１６】本発明のさらに他の形態においては、前記
第一及び第二の電極層が、InPで生成された半導体薄膜
層であり、かつ、前記光伝導半導体薄膜層がInGaAsで生
成される。In still another embodiment of the present invention, the first and second electrode layers are semiconductor thin film layers made of InP, and the photoconductive semiconductor thin film layer is made of InGaAs.
【００１７】本発明のさらに他の形態においては、前記
第一及び第二の電極層が、前記第一及び第二の電極層の
断面幅よりも広い幅にわたって互いに近接する近接部を
それぞれ有し、前記第一及び第二の電極層の上にそれぞ
れ形成された第一及び第二の電極とをさらに備える。In still another embodiment of the present invention, the first and second electrode layers have adjacent portions that are close to each other over a width wider than the cross-sectional width of the first and second electrode layers. And first and second electrodes respectively formed on the first and second electrode layers.
【００１８】なお上記の発明の概要は、本発明の必要な
特徴の全てを列挙したものではなく、これらの特徴群の
サブコンビネーションもまた発明となりうる。Note that the above summary of the present invention does not list all of the necessary features of the present invention, and a sub-combination of these features may also be an invention.
【００１９】[0019]
【発明の実施の形態】以下、発明の実施の形態を通じて
本発明を説明するが、以下の実施形態は特許請求の範囲
に係る発明を限定するものではなく、また実施形態の中
で説明されている特徴の組み合わせの全てが発明の解決
手段に必須であるとは限らない。DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments do not limit the invention according to the claims and are described in the embodiments. Not all combinations of features are essential to the solution of the invention.
【００２０】まず、フォトコンダクタの一つであるＭＳ
Ｍフォトコンダクタの構造と光伝導効果について以下説
明する。図３は、本実施形態のフォトコンダクタの断面
図である。図に示される通り、本実施形態のフォトコン
ダクタは、半導体基板１０と光伝導半導体薄膜層２０と
第一及び第二の電極用半導体薄膜層３０、３１と第一及
び第二の電極４０、４１とを備えるＭＳＭフォトコンダ
クタである。First, one of the photoconductors, MS
The structure of the M photoconductor and the photoconductive effect will be described below. FIG. 3 is a sectional view of the photoconductor of the present embodiment. As shown in the figure, the photoconductor of this embodiment includes a semiconductor substrate 10, a photoconductive semiconductor thin film layer 20, first and second electrode semiconductor thin film layers 30, 31, and first and second electrodes 40, 41. An MSM photoconductor comprising:
【００２１】半導体基板１０の上には光伝導半導体薄膜
層２０を成長させる。光伝導半導体薄膜層２０の上に
は、第一及び第二の電極用半導体薄膜層３０、３１をぞ
れぞれ成長させる。第一及び第二の電極用半導体薄膜層
３０、３１は、互いに所定の間隔を隔てて近接させる。
第一及び第二の電極用半導体薄膜層３０、３１の上には
それぞれ第一及び第二の電極４０、４１を蒸着させる。On the semiconductor substrate 10, a photoconductive semiconductor thin film layer 20 is grown. On the photoconductive semiconductor thin film layer 20, first and second electrode semiconductor thin film layers 30, 31 are grown, respectively. The first and second electrode semiconductor thin film layers 30 and 31 are brought close to each other at a predetermined interval.
First and second electrodes 40 and 41 are deposited on the first and second electrode semiconductor thin film layers 30 and 31, respectively.
【００２２】半導体に光が入射されたとき、光の持つフ
ォトンエネルギーが半導体の禁制帯幅よりも大きければ
その光はその半導体に吸収される。半導体に光が吸収さ
れると光励起により自由キャリアが生じるため、半導体
の抵抗は下がり導電率は増加する（光伝導効果）。本実
施形態のＭＳＭフォトコンダクタにおいては、消光状態
の抵抗（オフ抵抗Ｒｏｆｆ）は数十ＭΩｃｍであるのに
対し、照射状態の抵抗（オン抵抗Ｒｏｎ）は数十Ωｃｍ
以下まで下がる。When light is incident on a semiconductor and the photon energy of the light is larger than the bandgap of the semiconductor, the light is absorbed by the semiconductor. When light is absorbed by the semiconductor, free carriers are generated by photoexcitation, so that the resistance of the semiconductor decreases and the conductivity increases (photoconductive effect). In the MSM photoconductor of this embodiment, the resistance in the extinction state (off resistance R off ) is several tens MΩcm, whereas the resistance in the irradiation state (on resistance R on ) is several tens Ωcm.
Down to below.
【００２３】光伝導効果による導電率の変化は、伝導電
子が支配的な場合、 σphoto = σdark＋Δσ = ｅ・ｎ・μ＋ｅ・Δｎ・μ = ｅ・μ（ｎ＋Δｎ） ・・・式（２） となる。ここで、σphotoは照射状態の導電率、σdark
は消光状態の導電率、Δσは光照射による導電率の変化
分、ｅは電子の電荷量、μは電子の移動度、ｎはキャリ
ア密度、Δｎは光励起によるキャリア密度の変化分をそ
れぞれ示す。このように、光励起によりキャリアが生
じ、半導体の導電率が増加する。When the conduction electrons are dominant, the change in the conductivity due to the photoconductive effect is as follows: . Here, σphoto is the conductivity of the irradiated state, σdark
Is the conductivity in the quenched state, Δσ is the change in conductivity due to light irradiation, e is the charge amount of electrons, μ is the mobility of electrons, n is the carrier density, and Δn is the change in carrier density due to photoexcitation. As described above, carriers are generated by photoexcitation, and the conductivity of the semiconductor increases.
【００２４】オン抵抗Ｒｏｎの一般式は、 Ｒｏｎ＝（ｈυ・Ｌ２）／（ｑ・μ・τ・Ｐｏｐｔ・η） ・・・式（３ ） となる。ここで、ｈはプランク定数、νは光の振動度、
ｃは光の速度、Ｌは第一及び第二の電極用半導体薄膜層
３０、３１の間隔、ｑは電子の電荷量、μは電子の移動
度、τは電子の寿命、Ｐｏｐｔは光の入力パワー、ηは
量子効率をそれぞれ示す。量子効率ηは、 η＝Ｓ・（１−ｒ）・［１−ｅｘｐ（−α・ｔ）］ ・・・式（４） となる。ここで、Ｓは照射した光のうち光伝導半導体薄
膜層２０に入力される光の割合、ｒは光伝導半導体薄膜
層２０における光の反射率、ｔは光伝導半導体薄膜層２
０の薄膜厚をそれぞれ示す。The general formula of the on -resistance R on is as follows: R on = (hυ · L 2 ) / (q · μ · τ · P opt · η) (3) Here, h is Planck's constant, ν is the light vibration degree,
c is the speed of light, L is the interval between the first and second electrode semiconductor thin film layers 30 and 31, q is the charge of electrons, μ is the mobility of electrons, τ is the lifetime of electrons, and P opt is the light Input power and η indicate quantum efficiency, respectively. The quantum efficiency η is as follows: η = S · (1−r) · [1-exp (−α · t)] (4) Here, S is the ratio of light input to the photoconductive semiconductor thin film layer 20 among the irradiated light, r is the reflectance of light in the photoconductive semiconductor thin film layer 20, and t is the photoconductive semiconductor thin film layer 2.
The thin film thickness of 0 is shown.
【００２５】オン抵抗Ｒｏｎを低くする手段としては、
式（３）及び式（４）より、光のフォトンエネルギーｈ
νを小さくすること、光の波長λを長波長側に選択する
こと、電子の移動度μと電子の寿命τとを大きくするこ
と、吸収係数αを大きくすること、反射率ｒを小さくす
ること、半導体薄膜厚ｔを大きくすること等が挙げられ
る。これらのパラメータは半導体材料が持つ固有の特性
に基づいている。一方、電極構造を最適にすれば、どの
ような光伝導半導体を用いても、ＭＳＭフォトコンダク
タの応答性と感度を高めやすい。As means for reducing the on-resistance R on ,
From equations (3) and (4), the photon energy h of light
To reduce ν, to select the wavelength λ of light on the longer wavelength side, to increase the electron mobility μ and the electron lifetime τ, to increase the absorption coefficient α, and to reduce the reflectance r And increasing the thickness t of the semiconductor thin film. These parameters are based on the intrinsic properties of the semiconductor material. On the other hand, if the electrode structure is optimized, the responsiveness and sensitivity of the MSM photoconductor can be easily increased regardless of the type of photoconductive semiconductor used.
【００２６】半導体基板１０は、半絶縁性半導体材料で
形成される。本実施形態における半導体基板１０は、半
絶縁性半導体材料としてS.I.（Semi Insulator：半絶縁
性）InP（インジウム・リン）を用いたS.I.InP基板とし
た。半導体基板１０は、S.I.GaAs（半絶縁性ガリウム・
砒素）基板等の他の半絶縁性半導体基板とすることもで
きる。The semiconductor substrate 10 is formed of a semi-insulating semiconductor material. The semiconductor substrate 10 in the present embodiment is an SIInP substrate using semi-insulating (Semi Insulator) InP (indium phosphorus) as a semi-insulating semiconductor material. The semiconductor substrate 10 is made of SIGaAs (semi-insulating gallium
Another semi-insulating semiconductor substrate such as an arsenic substrate may be used.
【００２７】光伝導半導体薄膜層２０は、本実施形態に
おいてはInGaAs（インジウム・ガリウム・砒素）を用い
る。光伝導半導体薄膜層２０を形成する他の半導体材料
としては、Fe（鉄）をドーピングしたFeドープInP、GaA
s、LT-（Low Temprature：低温成長）GaAs、LT-InGaA
s、InGaAsとInAlAs（インジウム・アルミニウム・砒
素）との超格子構造、又は、InGaAsとInAlAsとのＭＱＷ
（Multi Quantum Well：多重量子井戸）構造等の超高速
光半導体を用いることもできる。これらの超高速光半導
体は波長１．５５μｍの長波長帯の光に対して十分に感
度が高く高速に応答する点に特徴があり、近年は光検出
器としてだけではなく、光ファイバ通信送受信器におけ
る光電変換等にも用いられる。In the present embodiment, the photoconductive semiconductor thin film layer 20 uses InGaAs (indium gallium arsenide). Other semiconductor materials forming the photoconductive semiconductor thin film layer 20 include Fe-doped InP, GaAs doped with Fe (iron).
s, LT- (Low Temprature), GaAs, LT-InGaA
s, super lattice structure of InGaAs and InAlAs (indium aluminum arsenic) or MQW of InGaAs and InAlAs
An ultrafast optical semiconductor having a (Multi Quantum Well) structure or the like can also be used. These ultrahigh-speed optical semiconductors are characterized in that they are sufficiently sensitive and respond quickly to light in the long wavelength band of 1.55 μm. It is also used for photoelectric conversion and the like.
【００２８】半導体基板１０の上に光伝導半導体薄膜層
２０を成長させるときに、組成の異なる半導体同士を接
合（ヘテロ接合）させることとなる。良好な成長を得る
ためには基板と薄膜層とのそれぞれの格子定数がほぼ一
致する（格子整合する）ことが望ましい。InGaAsはInP
に格子整合する半導体材料であり、本実施形態では、S.
I.InP基板の上にInGaAs薄膜層を成長させている。When the photoconductive semiconductor thin film layer 20 is grown on the semiconductor substrate 10, semiconductors having different compositions are joined (hetero junction). In order to obtain good growth, it is desirable that the lattice constants of the substrate and the thin film layer substantially match (lattice matching). InGaAs is InP
Is a semiconductor material lattice-matched to S. In this embodiment, S.
I. InGaAs thin film layer is grown on InP substrate.
【００２９】第一及び第二の電極用半導体薄膜層３０、
３１としては、光伝導半導体薄膜層２０に格子整合する
半導体材料を用いるのが望ましい。本実施形態では、第
一及び第二の電極用半導体薄膜層３０、３１として、In
Pを用いる。InPは光伝導半導体薄膜層２０に用いられる
InGaAsと格子整合する。第一及び第二の電極用半導体薄
膜層３０、３１として用いられるInPは、不純物がドー
ピングされた低抵抗半導体である。光照射時には光伝導
半導体薄膜層２０の抵抗が数十Ωｃｍ以下（オン抵抗Ｒ
ｏｎ）まで下がる。光伝導半導体薄膜層２０による光伝
導効果を最大に活かすためには第一及び第二の電極用半
導体薄膜層３０、３１の抵抗は、オン抵抗Ｒｏｎの値で
ある数１０Ωｃｍよりも十分に小さい値が望ましい。即
ち、第一及び第二の電極用半導体薄膜層３０、３１の導
電率は、光照射時の光伝導半導体薄膜層２０の導電率σ
photoより十分に高いことが望ましい。本実施形態にお
けるInPの抵抗は数Ωｃｍオーダーである。The first and second semiconductor thin film layers 30 for electrodes,
As 31, it is desirable to use a semiconductor material lattice-matched to the photoconductive semiconductor thin film layer 20. In the present embodiment, as the first and second electrode semiconductor thin film layers 30 and 31, In
Use P. InP is used for the photoconductive semiconductor thin film layer 20
Lattice matched with InGaAs. InP used as the first and second electrode semiconductor thin film layers 30 and 31 is a low-resistance semiconductor doped with impurities. At the time of light irradiation, the resistance of the photoconductive semiconductor thin film layer 20 is several tens Ωcm or less (on-resistance R
on ). In order to maximize the photoconductive effect of the photoconductive semiconductor thin film layer 20, the resistance of the first and second electrode semiconductor thin film layers 30, 31 is sufficiently smaller than the value of the on-resistance R on of several tens Ωcm. Values are desirable. That is, the electric conductivity of the first and second electrode semiconductor thin film layers 30 and 31 is the electric conductivity σ of the photoconductive semiconductor thin film layer 20 during light irradiation.
Desirably higher than photo. The resistance of InP in this embodiment is on the order of several Ωcm.
【００３０】第一及び第二の電極４０、４１は、本実施
形態においては、第一及び第二の電極用半導体薄膜層３
０、３１にそれぞれ接合するAuGe（金・ゲルマニウム）
層４０ｂ、４１ｂと、AuGe層４０ｂ、４１ｂの上にそれ
ぞれ形成されるAu（金）層４０ａ、４１ａとを有する。
AuGeは、第一及び第二の電極用半導体薄膜層３０、３１
に用いられるInPにオーミック接合させることができ
る。従って、第一の電極４０及び第二の電極用半導体薄
膜層３１、並びに、第二の電極４１及び第二の電極用半
導体薄膜層３１は、それぞれオーミック電極を形成す
る。In the present embodiment, the first and second electrodes 40 and 41 are formed of the first and second electrode semiconductor thin film layers 3.
AuGe (gold / germanium) bonded to 0 and 31, respectively
It has layers 40b and 41b, and Au (gold) layers 40a and 41a formed on the AuGe layers 40b and 41b, respectively.
AuGe is the first and second electrode semiconductor thin film layers 30, 31.
Ohmic junction with InP used for Therefore, the first electrode 40 and the second electrode semiconductor thin film layer 31, and the second electrode 41 and the second electrode semiconductor thin film layer 31 form ohmic electrodes, respectively.
【００３１】本実施形態によれば、光伝導半導体薄膜層
２０としてInGaAs等のオーミック電極を形成させること
が困難な半導体材料を用いた場合であっても、光伝導半
導体薄膜層２０の上にさらに他の半導体で薄膜層を形成
させてその上に電極を形成させる構成とすることによ
り、オーミック電極を形成させることができる。According to the present embodiment, even when a semiconductor material such as InGaAs, for which it is difficult to form an ohmic electrode, is used as the photoconductive semiconductor thin film layer 20, the photoconductive semiconductor thin film layer 20 An ohmic electrode can be formed by forming a thin film layer of another semiconductor and forming an electrode thereon.
【００３２】光伝導半導体薄膜層２０に光が照射される
と、光励起によりキャリアが生じて光伝導半導体薄膜層
２０の導電率が増加する。第一及び第二の電極４０、４
１に電圧を加えると、第一の電極４０と第二の電極４１
の間を、第一及び第二の電極用半導体薄膜層３０、３１
と光伝導半導体薄膜層２０とを介して電流が流れる。第
一及び第二の電極用半導体薄膜層３０、３１は低抵抗半
導体であり、かつ、第一の電極４０及び第二の電極用半
導体薄膜層３１、並びに、第二の電極４１及び第二の電
極用半導体薄膜層３１は、それぞれオーミック接合す
る。従って、第一及び第二の電極４０、４１と光伝導半
導体薄膜層２０との間に電位障壁は形成されず、ＭＳＭ
フォトコンダクタの高速応答特性が阻害されない。When the photoconductive semiconductor thin film layer 20 is irradiated with light, carriers are generated by photoexcitation, and the conductivity of the photoconductive semiconductor thin film layer 20 increases. First and second electrodes 40, 4
When a voltage is applied to 1, the first electrode 40 and the second electrode 41
Between the first and second electrode semiconductor thin film layers 30, 31
An electric current flows through and the photoconductive semiconductor thin film layer 20. The first and second electrode semiconductor thin film layers 30 and 31 are low-resistance semiconductors, and the first electrode 40 and the second electrode semiconductor thin film layer 31, and the second electrode 41 and the second The electrode semiconductor thin-film layers 31 are in ohmic contact with each other. Therefore, no potential barrier is formed between the first and second electrodes 40 and 41 and the photoconductive semiconductor thin film layer 20, and the MSM
High-speed response characteristics of the photoconductor are not hindered.
【００３３】図４は、光伝導半導体薄膜層２０と第一及
び第二の電極用半導体薄膜層３０、３１の光吸収特性を
示す。光伝導半導体薄膜層２０に照射する光について以
下説明する。半導体は、その禁制帯幅より大きいフォト
ンエネルギーを持つ光を吸収する（光吸収特性）。言い
換えれば、半導体は、所定の波長（吸収端波長）以下の
波長を有する光を吸収する。光のフォトンエネルギーを
ｈυ（ｈはプランク定数、υは光の振動数）［ｅＶ］と
し、光の波長をλ［μｍ］とすると、ｈυ＝ｈｃ／λ＝
１．２４／λの関係となる（ｃは光の速度）。半導体の
禁制帯幅をＥｇ［ｅＶ］とし、半導体の吸収端波長をλ
ｇ［μｍ］とすると、Ｅｇ＝１．２４／λｇとなる。そ
して、半導体に吸収される光とその半導体の間には、ｈ
υ＞Ｅｇ、λ≦λｇの関係が成り立つ。吸収端波長より
長い波長の光は半導体に吸収されず透過する。FIG. 4 shows light absorption characteristics of the photoconductive semiconductor thin film layer 20 and the first and second electrode semiconductor thin film layers 30 and 31. The light applied to the photoconductive semiconductor thin film layer 20 will be described below. A semiconductor absorbs light having a photon energy larger than its band gap (light absorption characteristic). In other words, the semiconductor absorbs light having a wavelength equal to or less than a predetermined wavelength (absorption edge wavelength). Assuming that the photon energy of light is hυ (h is Planck's constant, 光 is the frequency of light) [eV] and the wavelength of light is λ [μm], hυ = hc / λ =
The relationship is 1.24 / λ (c is the speed of light). The bandgap of the semiconductor is Eg [eV], and the absorption edge wavelength of the semiconductor is λ.
If g [μm], Eg = 1.24 / λg. And, between light absorbed by the semiconductor and the semiconductor, h
υ> Eg, λ ≦ λg holds. Light having a wavelength longer than the absorption edge wavelength is transmitted through the semiconductor without being absorbed.
【００３４】光吸収特性及び吸収端波長は半導体材料に
より異なる。光伝導半導体薄膜層２０に用いる半導体材
料の吸収端波長をλｇｐｃ［μｍ］とし、第一及び第二
の電極用半導体薄膜層３０、３１に用いる半導体材料の
吸収端波長をλｇｏｈｍｉｃ［μｍ］とする。例えば、
λｇｏｈｍｉｃがλｇｐｃよりも短い場合、λｇｏｈ
ｍｉｃより長くλｇｐｃより短い波長を有する照射光は
第一及び第二の電極用半導体薄膜層３０、３１を透過し
て光伝導半導体薄膜層２０に吸収される。このとき、第
一及び第二の電極用半導体薄膜層３０、３１は光に対し
て透明な窓に相当する。The light absorption characteristics and the absorption edge wavelength differ depending on the semiconductor material. The absorption edge wavelength of the semiconductor material used for the photoconductive semiconductor thin film layer 20 is λg pc [μm], and the absorption edge wavelength of the semiconductor material used for the first and second electrode semiconductor thin film layers 30 and 31 is λg ohmic [μm]. And For example,
If λg ohmic is shorter than λg pc, λg oh
Irradiation light having a wavelength longer than mic and shorter than λg pc passes through the first and second electrode semiconductor thin film layers 30 and 31 and is absorbed by the photoconductive semiconductor thin film layer 20. At this time, the first and second electrode semiconductor thin film layers 30 and 31 correspond to windows transparent to light.
【００３５】波長λ［μｍ］の光を第一及び第二の電極
用半導体薄膜層３０、３１を透過させて光伝導半導体薄
膜層２０に吸収させるためには、光伝導半導体薄膜層２
０としてλ以上の波長に吸収端がある半導体材料を選択
し、第一及び第二の電極用半導体薄膜層３０、３１とし
てλ未満に吸収端がある半導体材料を選択する。即ち、
波長λ［μｍ］の光を第一及び第二の電極用半導体薄膜
層３０、３１を透過させて光伝導半導体薄膜層２０だけ
に吸収させるためには、光伝導半導体薄膜層２０として
１．２４／λ未満の禁制帯幅を有する半導体材料を選択
し、第一及び第二の電極用半導体薄膜層３０、３１とし
て１．２４／λ以上の禁制帯幅を有する半導体材料を選
択する。In order to allow the light of wavelength λ [μm] to pass through the first and second electrode semiconductor thin film layers 30 and 31 and to be absorbed by the photoconductive semiconductor thin film layer 20, the light conductive semiconductor thin film layer 2
A semiconductor material having an absorption edge at a wavelength of λ or more is selected as 0, and a semiconductor material having an absorption edge below λ is selected as the first and second electrode semiconductor thin film layers 30 and 31. That is,
In order to allow the light of wavelength λ [μm] to pass through the first and second electrode semiconductor thin film layers 30 and 31 and to be absorbed only by the photoconductive semiconductor thin film layer 20, the photoconductive semiconductor thin film layer 20 must have a thickness of 1.24. A semiconductor material having a band gap of less than / λ is selected, and a semiconductor material having a band gap of 1.24 / λ or more is selected as the first and second electrode semiconductor thin film layers 30 and 31.
【００３６】図４において、横軸が照射される光の波長
λ［μｍ］を表し、縦軸が吸収係数α［ｃｍ−１］を表
す。吸収係数αは、光が半導体中を進行しながら吸収に
より減衰していく割合を示す。光の強度をＧとすると、
α＝（−１／Ｇ）・（ｄＧ／ｄｔ）となる。In FIG. 4, the horizontal axis represents the wavelength λ [μm] of the irradiated light, and the vertical axis represents the absorption coefficient α [cm −1 ]. The absorption coefficient α indicates a rate at which light attenuates due to absorption while traveling in the semiconductor. If the light intensity is G,
α = (− 1 / G) · (dG / dt).
【００３７】図に示される通り、照射される光の波長λ
が半導体の吸収端波長よりわずかに短いときは吸収係数
αは低いが（基礎吸収）、波長λが短くなるにつれて吸
収係数αが急激に大きくなる。半導体の受光効率を高め
るためには、吸収特性αが最も大きくなる波長、即ち吸
収端波長よりも少し短い波長の光を照射するのがよい。As shown in the figure, the wavelength λ of the irradiated light
Is slightly shorter than the absorption edge wavelength of the semiconductor, the absorption coefficient α is low (basic absorption), but as the wavelength λ becomes shorter, the absorption coefficient α rapidly increases. In order to increase the light receiving efficiency of the semiconductor, it is preferable to irradiate light having a wavelength at which the absorption characteristic α is maximized, that is, light having a wavelength slightly shorter than the absorption edge wavelength.
【００３８】図４（ａ）は光伝導半導体薄膜層２０の光
吸収特性を示し、図４（ｂ）は第一及び第二の電極用半
導体薄膜層３０、３１の光吸収特性を示す。本実施形態
においては、光伝導半導体薄膜層２０にInGaAsが用いら
れ、第一及び第二の電極用半導体薄膜層３０、３１にIn
Pが用いられる。光伝導半導体薄膜層２０の吸収端波長
をλｇｐｃとし、第一及び第二の電極用半導体薄膜層３
０、３１の吸収端波長をλｇｏｈｍｉｃとすると、λｇ
ｏｈｍｉｃ＜λｇｐｃとなる。例えば、光伝導半導体薄
膜層２０の吸収端波長λｇｐｃが１．５５μｍより長
く、第一及び第二の電極用半導体薄膜層３０、３１の吸
収端波長λｇｏｈｍｉｃが１．５５μｍより短い場合、
波長λｉ＝１．５５μｍの照射光は、第一及び第二の電
極用半導体薄膜層３０、３１を透過して光伝導半導体薄
膜層２０に吸収される。FIG. 4A shows the light absorption characteristics of the photoconductive semiconductor thin film layer 20, and FIG. 4B shows the light absorption characteristics of the first and second electrode semiconductor thin film layers 30, 31. In this embodiment, InGaAs is used for the photoconductive semiconductor thin film layer 20, and InGaAs is used for the first and second electrode semiconductor thin film layers 30, 31.
P is used. The absorption edge wavelength of the photoconductive semiconductor thin film layer 20 is λg pc and the first and second electrode semiconductor thin film layers 3
Assuming that the absorption edge wavelengths of 0 and 31 are λg ohmic , λg
ohmic <λg pc . For example, when the absorption edge wavelength λg pc of the photoconductive semiconductor thin film layer 20 is longer than 1.55 μm, and the absorption edge wavelength λg ohmic of the first and second electrode semiconductor thin film layers 30 and 31 is shorter than 1.55 μm,
The irradiation light having the wavelength λi = 1.55 μm passes through the first and second electrode semiconductor thin film layers 30 and 31 and is absorbed by the photoconductive semiconductor thin film layer 20.
【００３９】波長λｉの光が第一及び第二の電極用半導
体薄膜層３０、３１を透過して光伝導半導体薄膜層２０
に吸収される場合、第一及び第二の電極用半導体薄膜層
３０、３１の上から照射した波長λｉの光は、ほぼ全て
光伝導半導体薄膜層２０に入力される。従って、光の照
射量に対する光伝導半導体薄膜層２０の受光量の割合が
高くなり、ＭＳＭフォトコンダクタの感度を高められ
る。The light having the wavelength λi passes through the first and second electrode semiconductor thin film layers 30 and 31 and passes through the photoconductive semiconductor thin film layer 20.
When light is absorbed into the photoconductive semiconductor thin film layer 20, almost all of the light having the wavelength λi irradiated from above the first and second electrode semiconductor thin film layers 30 and 31 is input to the photoconductive semiconductor thin film layer 20. Therefore, the ratio of the amount of light received by the photoconductive semiconductor thin film layer 20 to the amount of light irradiation increases, and the sensitivity of the MSM photoconductor can be increased.
【００４０】本実施形態において光伝導半導体薄膜層２
０に用いられるInGaAsは、波長１．５５μｍの光に対し
て感度が高い。一方、第一及び第二の電極用半導体薄膜
層３０、３１に用いられるInPは、波長１．５５μｍの
光を透過させる。従って、本実施形態のＭＳＭフォトコ
ンダクタは、波長１．５５μｍの光が利用される光ファ
イバ通信における光電変換等に適する。In this embodiment, the photoconductive semiconductor thin film layer 2
InGaAs used for 0 has high sensitivity to light having a wavelength of 1.55 μm. On the other hand, InP used for the first and second electrode semiconductor thin film layers 30 and 31 transmits light having a wavelength of 1.55 μm. Therefore, the MSM photoconductor of the present embodiment is suitable for photoelectric conversion in optical fiber communication using light having a wavelength of 1.55 μm.
【００４１】図５は、本実施形態におけるフォトコンダ
クタの平面図である。図に示される通り、本実施形態に
おける第一及び第二の電極用半導体薄膜層３０、３１の
構造として、櫛型構造が用いられる。櫛型構造とは、第
一の電極用半導体薄膜層３０と第二の電極用半導体薄膜
層３１とが対向する櫛状の突片をそれぞれ有し、各突片
同士が互い違いに形成される構造である。櫛型構造を用
いると、第一の電極用半導体薄膜層３０が第二の電極用
半導体薄膜層３１に近接する面の幅がそれぞれの断面幅
Ｗｓよりも広くなる。これにより、第一の電極用半導体
薄膜層３０と第二の電極用半導体薄膜層３１との間に生
じる電界が多く生ずる。FIG. 5 is a plan view of the photoconductor according to the present embodiment. As shown in the drawing, a comb structure is used as the structure of the first and second electrode semiconductor thin film layers 30 and 31 in the present embodiment. The comb structure has a structure in which the first semiconductor thin film layer 30 for electrodes and the second semiconductor thin film layer 31 for electrodes each have a comb-shaped protrusion, and the protrusions are formed alternately. It is. When the comb-shaped structure is used, the width of the surface of the first semiconductor thin film layer 30 for the electrode close to the second semiconductor thin film layer 31 becomes wider than the cross-sectional width Ws. As a result, a large electric field is generated between the first electrode semiconductor thin film layer 30 and the second electrode semiconductor thin film layer 31.
【００４２】第一及び第二の電極用半導体薄膜層３０、
３１は、互いに近接する部分においてそれぞれ近接部３
２ａ、３２ｂを有する。近接部３２ａ、３２ｂは、互い
に対向する方向に延びる複数の突片を含む。近接部３２
ａの各突片は、近接部３２ｂの各突片に所定の間隔Ｌで
近接し、互い違いに形成される。近接部３２ａ、３２ｂ
の各突片の幅Ｗは数μｍである。近接部３２ａは近接部
３２ｂに対し、第一及び第二の電極用半導体薄膜層３
０、３１の断面幅Ｗｓよりも広い幅にわたって互いに近
接する。各突片の長さ（交差長）は、長いほど電界が多
く生ずる。The first and second electrode semiconductor thin film layers 30,
Reference numerals 31 denote proximity portions 3 in portions close to each other.
2a and 32b. The proximity portions 32a and 32b include a plurality of protruding pieces extending in directions facing each other. Proximity 32
Each protruding piece of a is adjacent to each protruding piece of the proximity portion 32b at a predetermined interval L, and is formed alternately. Proximities 32a, 32b
The width W of each protruding piece is several μm. The proximity portion 32a is different from the proximity portion 32b by the first and second electrode semiconductor thin film layers 3.
0 and 31 are close to each other over a width wider than the cross-sectional width Ws. The longer the length of each protruding piece (crossing length), the more electric field is generated.
【００４３】オン抵抗Ｒｏｎは、式（３）に示される通
り、近接部３２ａと近接部３２ｂとの間隔Ｌの２乗に比
例するため、間隔Ｌが小さいほどオン抵抗は低くなる。
間隔Ｌは数μｍオーダー、又は、１μｍ以下が望まし
い。As shown in the equation (3), the on-resistance R on is proportional to the square of the distance L between the adjacent parts 32a and 32b. Therefore, the smaller the distance L, the lower the on-resistance.
The interval L is desirably on the order of several μm, or 1 μm or less.
【００４４】第一及び第二の電極用半導体薄膜層３０、
３１の光吸収端波長が光伝導半導体薄膜層２０の光吸収
端波長よりも短い場合、照射された光のほぼ全てが第一
及び第二の電極用半導体薄膜層３０、３１を透過し光伝
導半導体薄膜層２０に吸収される。即ち、照射された光
は、第一の電極用半導体薄膜層３０と第二の電極用半導
体薄膜層３１との間隔Ｌの部分だけでなく、近接部３２
ａ、３２ｂに含まれる各突片の幅Ｗの部分も透過する。The first and second electrode semiconductor thin film layers 30,
When the light absorption edge wavelength of the light absorption edge 31 is shorter than the light absorption edge wavelength of the photoconductive semiconductor thin film layer 20, almost all of the irradiated light is transmitted through the first and second electrode semiconductor thin film layers 30 and 31 and the photoconductive It is absorbed by the semiconductor thin film layer 20. That is, the irradiated light is emitted not only at the distance L between the first electrode semiconductor thin film layer 30 and the second electrode semiconductor thin film layer 31 but also at the proximity portion 32.
The portions of the width W of each protruding piece included in a and 32b are also transmitted.
【００４５】以上のように、近接部３２ａ、３２ｂを櫛
型構造にして第一の電極用半導体薄膜層３０が第二の電
極用半導体薄膜層３１に近接し対向する面の幅を広くし
たことにより、電界が多く生じＭＳＭフォトコンダクタ
の高速化を図ることができる。さらに、光伝導半導体薄
膜層２０に吸収させる光が第一及び第二の電極用半導体
薄膜層３０、３１を透過する場合、近接部３２ａ、３２
ｂの形状を各突片の幅Ｗを狭くせずに櫛型構造等を形成
させることができる。また、近接部３２ａと近接部３２
ｂとの間隔Ｌを狭くしても照射光が光伝導半導体薄膜層
２０へ入力される割合Ｓは低下しない。As described above, the proximity portions 32a and 32b have a comb-shaped structure, and the width of the surface where the first semiconductor thin film layer 30 is close to and opposed to the second semiconductor thin film layer 31 is widened. As a result, many electric fields are generated and the speed of the MSM photoconductor can be increased. Further, when the light to be absorbed by the photoconductive semiconductor thin film layer 20 passes through the first and second electrode semiconductor thin film layers 30 and 31, the proximity portions 32a and 32
A comb-shaped structure or the like can be formed without reducing the width b of each protruding piece in the shape of b. In addition, the proximity portion 32a and the proximity portion 32
Even if the interval L with respect to b is narrowed, the ratio S of irradiation light input to the photoconductive semiconductor thin film layer 20 does not decrease.
【００４６】本実施形態においては、第一及び第二の電
極用半導体薄膜層３０、３１の近接部３２ａ、３２ｂの
構造として櫛型構造を用いるが、他の構造を用いてもよ
い。他の構造には、近接部３２ａの突片と近接部３２ｂ
の突片とを並行に螺旋状に形成させるスパイラル型や、
近接部３２ａ、３２ｂに突片を設けず、近接部３２ａ、
３２ｂを互いに並行に対向させる対向型等の構造があ
る。In this embodiment, a comb-shaped structure is used as the structure of the adjacent portions 32a and 32b of the first and second electrode semiconductor thin film layers 30 and 31, but another structure may be used. Other structures include a protruding piece of the proximity portion 32a and a proximity portion 32b.
Spiral type to form a spiral in parallel with the protruding piece,
No protruding piece is provided in the proximity portions 32a, 32b,
There is a structure such as a facing type in which the 32b is opposed to each other in parallel.
【００４７】以上のように、本実施形態によれば、光伝
導半導体薄膜層２０としてInGaAs等のオーミック電極を
形成させることが困難な半導体材料を用いた場合であっ
ても、光伝導半導体薄膜層２０の上に他の半導体を用い
た薄膜層をさらに形成させてその上に電極を形成させる
構成とすることにより、オーミック電極を形成させるこ
とができる。As described above, according to the present embodiment, even when a semiconductor material such as InGaAs which is difficult to form an ohmic electrode is used as the photoconductive semiconductor thin film layer 20, the photoconductive semiconductor thin film layer An ohmic electrode can be formed by further forming a thin film layer using another semiconductor on 20 and forming an electrode thereon.
【００４８】また、本実施形態によれば、第一及び第二
の電極用半導体薄膜層３０、３１は低抵抗半導体であ
り、かつ、第一の電極４０及び第二の電極用半導体薄膜
層３１、並びに、第二の電極４１及び第二の電極用半導
体薄膜層３１は、それぞれオーミック接合するので、第
一及び第二の電極４０、４１と光伝導半導体薄膜層２０
との間に電位障壁は形成されず、ＭＳＭフォトコンダク
タの高速応答特性が阻害されない。Further, according to the present embodiment, the first and second electrode semiconductor thin film layers 30 and 31 are low-resistance semiconductors, and the first electrode 40 and the second electrode semiconductor thin film layer 31 are formed. Since the second electrode 41 and the second electrode semiconductor thin film layer 31 are in ohmic contact with each other, the first and second electrodes 40 and 41 and the photoconductive semiconductor thin film layer 20
And no potential barrier is formed between them, and the high-speed response characteristics of the MSM photoconductor are not hindered.
【００４９】また、本実施形態によれば、第一及び第二
の電極用半導体薄膜層３０、３１として、光伝導半導体
薄膜層２０に用いる半導体材料の光吸収端波長よりも短
い光吸収端波長の半導体材料を用いることにより、光伝
導半導体薄膜層２０にとって感度が高い所定の波長の光
を照射した場合、その光を第一及び第二の電極用半導体
薄膜層３０、３１に透過させて光伝導半導体薄膜層２０
に吸収させることができる。また、その場合、第一及び
第二の電極用半導体薄膜層３０、３１の上から照射した
光は、ほとんど全て光伝導半導体薄膜層２０に吸収され
るので、光の照射量に対する光伝導半導体薄膜層２０の
受光量の割合が高くなり、ＭＳＭフォトコンダクタの感
度を高めることができる。According to this embodiment, the first and second electrode semiconductor thin film layers 30 and 31 have a light absorption edge wavelength shorter than the light absorption edge wavelength of the semiconductor material used for the photoconductive semiconductor thin film layer 20. When the semiconductor material is irradiated with light of a predetermined wavelength which is highly sensitive to the photoconductive semiconductor thin film layer 20, the light is transmitted through the first and second electrode semiconductor thin film layers 30 and 31, and Conductive semiconductor thin film layer 20
Can be absorbed. Further, in this case, since the light irradiated from above the first and second electrode semiconductor thin film layers 30 and 31 is almost entirely absorbed by the photoconductive semiconductor thin film layer 20, the photoconductive semiconductor thin film with respect to the light irradiation amount The ratio of the amount of light received by the layer 20 increases, and the sensitivity of the MSM photoconductor can be increased.
【００５０】以上、本発明を実施の形態を用いて説明し
たが、本発明の技術的範囲は上記実施の形態に記載の範
囲には限定されない。上記実施の形態に、多様な変更又
は改良を加えることができることが当業者に明らかであ
る。その様な変更又は改良を加えた形態も本発明の技術
的範囲に含まれ得ることが、特許請求の範囲の記載から
明らかである。Although the present invention has been described with reference to the embodiment, the technical scope of the present invention is not limited to the scope described in the above embodiment. It is apparent to those skilled in the art that various changes or improvements can be added to the above embodiment. It is apparent from the description of the appended claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.
【発明の効果】上記説明から明らかなように、本発明に
よればＭＳＭフォトコンダクタを高速化又は高感度化す
ることができる。As is apparent from the above description, according to the present invention, the speed or sensitivity of the MSM photoconductor can be increased.
【図１】従来のフォトコンダクタの断面図である。FIG. 1 is a cross-sectional view of a conventional photoconductor.
【図２】図２は、従来のフォトコンダクタの平面図であ
る。FIG. 2 is a plan view of a conventional photoconductor.
【図３】本実施形態のフォトコンダクタの断面図であ
る。FIG. 3 is a cross-sectional view of the photoconductor of the present embodiment.
【図４】光伝導半導体薄膜層２０と第一及び第二の電極
用半導体薄膜層３０、３１の光吸収特性を示す。FIG. 4 shows light absorption characteristics of the photoconductive semiconductor thin film layer 20 and the first and second electrode semiconductor thin film layers 30 and 31.
【図５】本実施形態におけるフォトコンダクタの平面図
である。FIG. 5 is a plan view of a photoconductor according to the present embodiment.
１０ 半導体基板 ２０ 光伝導半導体薄膜層 ３０ 第一の電極用半導体薄膜層 ３１ 第二の電極用半導体薄膜層 ３２ａ、３２ｂ 近接部 ４０ 第一の電極 ４０ａ Au層 ４０ｂ AuGe層 ４１ 第二の電極 ４１ａ Au層 ４１ｂ AuGe層 ５０ 第一の電極 ５１ 第二の電極 ５２ａ、５２ｂ 電極近接部 DESCRIPTION OF SYMBOLS 10 Semiconductor substrate 20 Photoconductive semiconductor thin film layer 30 First semiconductor thin film layer 31 Second electrode semiconductor thin film layer 32a, 32b Proximity 40 First electrode 40a Au layer 40b AuGe layer 41 Second electrode 41a Au Layer 41b AuGe layer 50 First electrode 51 Second electrode 52a, 52b Electrode proximity
Claims (10)
するフォトコンダクタであって、 半導体基板上に形成され、所定の波長の光が照射された
場合に導電率が増加する光伝導半導体薄膜層と、 前記光伝導半導体薄膜層の上に形成され、所定の間隔を
隔てて互いに近接する第一及び第二の電極用半導体薄膜
層と、 前記第一及び第二の電極用半導体薄膜層の上にそれぞれ
形成された第一及び第二の電極とを備えることを特徴と
するフォトコンダクタ。1. A photoconductor having a conductivity that increases when irradiated with light, wherein the photoconductive semiconductor thin film is formed on a semiconductor substrate and increases in conductivity when irradiated with light having a predetermined wavelength. Layers, first and second electrode semiconductor thin film layers formed on the photoconductive semiconductor thin film layer and adjacent to each other at a predetermined interval, and of the first and second electrode semiconductor thin film layers. A photoconductor comprising: first and second electrodes respectively formed thereon.
の導電率は、前記光が照射された場合の前記光伝導半導
体薄膜層の導電率より高いことを特徴とする請求項１に
記載のフォトコンダクタ。2. The method according to claim 1, wherein the conductivity of the first and second electrode semiconductor thin film layers is higher than the conductivity of the photoconductive semiconductor thin film layer when the light is irradiated. The photoconductor as described.
は、それぞれ前記第一及び第二の電極にオーミック接合
することを特徴とする請求項１又は２に記載のフォトコ
ンダクタ。3. The photoconductor according to claim 1, wherein the first and second electrode semiconductor thin film layers are in ohmic contact with the first and second electrodes, respectively.
され、 前記第一及び第二の電極用半導体薄膜層がInPで生成さ
れることを特徴とする請求項１乃至３のいずれかに記載
のフォトコンダクタ。4. The photoconductive semiconductor thin film layer is made of InGaAs, and the first and second electrode semiconductor thin film layers are made of InP. Photo conductor.
がInPで生成され、 前記第一及び第二の電極が、前記第一及び第二の電極用
半導体薄膜層に接合するAuGe層と、前記AuGe層の上に形
成されるAu層とを有することを特徴とする請求項１乃至
４のいずれかに記載のフォトコンダクタ。5. The AuGe layer wherein the first and second electrode semiconductor thin film layers are formed of InP, and wherein the first and second electrodes are joined to the first and second electrode semiconductor thin film layers. The photoconductor according to claim 1, further comprising: an Au layer formed on the AuGe layer.
が、前記第一及び第二の電極用半導体薄膜層の断面幅よ
りも広い幅にわたって互いに近接する近接部をそれぞれ
有することを特徴とする請求項１乃至５のいずれかに記
載のフォトコンダクタ。6. The semiconductor thin film layers for the first and second electrodes each have adjacent portions that are close to each other over a width wider than the cross-sectional width of the semiconductor thin film layers for the first and second electrodes. The photoconductor according to any one of claims 1 to 5, wherein
するフォトコンダクタであって、 半導体基板上に形成され、所定の波長の光が照射された
場合に導電率が増加する光伝導半導体薄膜層と、 前記光伝導半導体薄膜層の上に形成され、所定の間隔を
隔てて互いに近接し、かつ、前記光を透過させる導体又
は半導体で生成された第一及び第二の電極層とを備える
ことを特徴とするフォトコンダクタ。7. A photoconductor having a conductivity that increases when irradiated with light, wherein the photoconductive semiconductor thin film is formed on a semiconductor substrate and increases in conductivity when irradiated with light of a predetermined wavelength. And a first and second electrode layer formed on the photoconductive semiconductor thin film layer, adjacent to each other at a predetermined interval, and formed of a conductor or a semiconductor that transmits the light. A photoconductor characterized by the above-mentioned.
生成された半導体薄膜層であり、前記第一及び第二の電
極層を形成する半導体薄膜層の光吸収端波長が、前記光
伝導半導体薄膜層の光吸収端波長より短いことを特徴と
する請求項７に記載のフォトコンダクタ。8. The semiconductor device according to claim 1, wherein the first and second electrode layers are semiconductor thin film layers formed of a semiconductor, and the light absorption edge wavelengths of the semiconductor thin film layers forming the first and second electrode layers are the same. The photoconductor according to claim 7, wherein the photoconductor is shorter than a light absorption edge wavelength of the photoconductive semiconductor thin film layer.
成された半導体薄膜層であり、かつ、前記光伝導半導体
薄膜層がInGaAsで生成されることを特徴とする請求項７
又は８に記載のフォトコンダクタ。9. The semiconductor device according to claim 7, wherein the first and second electrode layers are semiconductor thin film layers made of InP, and the photoconductive semiconductor thin film layer is made of InGaAs.
Or the photoconductor according to 8.
一及び第二の電極層の断面幅よりも広い幅にわたって互
いに近接する近接部をそれぞれ有し、 前記第一及び第二の電極層の上にそれぞれ形成された第
一及び第二の電極とをさらに備えることを特徴とする請
求項７乃至９のいずれかに記載のフォトコンダクタ。10. The first and second electrode layers each have adjacent portions that are close to each other over a width wider than the cross-sectional width of the first and second electrode layers, The photoconductor according to any one of claims 7 to 9, further comprising a first electrode and a second electrode formed on the electrode layer, respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09944399A JP4141582B2 (en) | 1999-04-06 | 1999-04-06 | Photo conductor |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09944399A JP4141582B2 (en) | 1999-04-06 | 1999-04-06 | Photo conductor |
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| Publication Number | Publication Date |
|---|---|
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| JP4141582B2 JP4141582B2 (en) | 2008-08-27 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002043592A (en) * | 2000-05-19 | 2002-02-08 | Agilent Technol Inc | Photoconductive switch |
| CN111564511A (en) * | 2020-05-19 | 2020-08-21 | 河北工业大学 | A kind of AlGaN-MSM detector structure based on polarization effect and its preparation method |
-
1999
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002043592A (en) * | 2000-05-19 | 2002-02-08 | Agilent Technol Inc | Photoconductive switch |
| CN111564511A (en) * | 2020-05-19 | 2020-08-21 | 河北工业大学 | A kind of AlGaN-MSM detector structure based on polarization effect and its preparation method |
| CN111564511B (en) * | 2020-05-19 | 2023-03-21 | 河北工业大学 | AlGaN-MSM detector structure based on polarization effect and preparation method thereof |
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