JPH10242500A - Monolithic light emitting / receiving element and optical pickup using the same - Google Patents

Abstract

(57) [Problem] To provide a monolithic light emitting / receiving element capable of ensuring both laser oscillation characteristics in a light emitting section and light-current conversion efficiency in a light receiving section. A light emitting unit and a light receiving unit are formed in at least two regions on a high-resistance semiconductor substrate. The light emitting unit 100A is a vertical cavity surface emitting laser 1
00A1 and a PIN photodiode 100A2, and the output light amount of 100A1 is monitored by 100A2.
The light receiving section 100B is composed of a PIN photodiode having a resonator structure, and the length of the resonator is 100A at room temperature.
It is configured to resonate with the wavelength of one outgoing light. The lower mirror of the portion 100A2 is removed by forming a hole 120 in this portion and the portion of the semiconductor substrate 101.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic light emitting / receiving element in which a light emitting element and a light receiving element are integrated on the same semiconductor substrate, and an optical pickup using the same.

[0002]

2. Description of the Related Art An optical pickup that records and reproduces information using light, for example, is known as a device that uses a light receiving unit such as a photodiode and a light emitting unit such as a semiconductor laser in a pair. In this technique, laser light from a semiconductor laser is made incident on a recording medium, and the reflected light is detected by a light receiving unit to record and reproduce information.

In recent years, various studies have been made to reduce the size and simplification of the optical pickup. One of the studies is to integrate a light emitting element and a light receiving element on the same semiconductor substrate. I have. Above all, a vertical cavity surface emitting laser (hereinafter, VCSEL: Vertical Cavi) in which a light source emits laser light in a direction perpendicular to the semiconductor substrate and a resonator is formed in a direction perpendicular to the semiconductor substrate.
ty Surface Emitting Laser), and the light receiving element is a photodiode having the same resonator structure as that of the VCSEL, and the light source and the light receiving element are monolithically integrated. In particular, attention has been paid to the degree of freedom in the layout of light emitting elements. As this monolithic light emitting / receiving element, for example, Electron
ics Letters 20th June 199
6 Vol. 32 No. 13 pp. 1205-12
What is disclosed at 07 is known. As shown in FIG. 11, a lower distributed reflection type multilayer mirror 302, an active region 303 composed of a multiple quantum well active layer sandwiched between cladding layers, and an upper distributed reflection type multilayer mirror 304 are sequentially formed on a semiconductor substrate 301 as shown in FIG. Grown, and then the upper distributed reflection type multilayer mirror 3 in the portion 300B where the light receiving element is formed.
The light receiving sensitivity of the photodiode is optimized by removing a part of the substrate 04 by chemical etching.

As described above, since the light receiving portion and the light emitting portion are formed by crystal growth on the same substrate at the same time, the positional relationship between the light receiving portion and the light emitting portion is determined by the patterning accuracy in the photolithography process, and is high. Position accuracy can be ensured.
In addition, by using a photodiode having a resonator structure as the light receiving section, not only the light receiving sensitivity is improved, but also the wavelength band of the light receiving sensitivity can be narrowed, and noise such as external light can be reduced. have.

However, according to the study of the present inventors, the optimum conditions required for the same crystal growth layer are different between the light emitting portion and the light receiving portion, and the process conditions suitable for one of the device characteristics are different. When the crystal growth layer is formed by the above, there is a problem that the other element characteristics are deteriorated. In particular, when crystal growth is performed under process conditions that match the element characteristics of the light emitting unit, the sensitivity of the light receiving unit is deteriorated, and it is not possible to accurately detect weak intensity light at the light receiving unit.

In order to solve this problem, the present inventors have disclosed in Japanese Patent Application No. Hei 7-198203 a surface-emitting type semiconductor laser having a light receiving portion having a structure in which a VCSEL is stacked on a PN type photodiode. .

[0007]

However, in this structure, since the photodiode does not have a resonator structure, a high light receiving sensitivity cannot be obtained, and there is an advantage that the photodiode is resistant to noise due to the resonator structure. Absent. Furthermore, since it is a PN-type photodiode, there is a problem that the response speed to high-speed modulated light is limited.

The present invention has been made to solve such a problem, and an object of the present invention is to form a light emitting section and a light receiving section on the same substrate, and obtain good laser oscillation characteristics in the light emitting section. It is an object of the present invention to provide a monolithic light emitting / receiving element having a light receiving section which has high sensitivity characteristics, can reduce noise such as external light, and has a high response speed, and an optical pickup using the same.

[0009]

According to a first monolithic light emitting / receiving element of the present invention, a first conductive type semiconductor layer and a second conductive type semiconductor layer are formed in at least two regions on a high resistance semiconductor substrate. Are formed by laminating a plurality of layers, and a first PIN is formed in one region by the first and second conductive semiconductor layers.
Photodiode and a vertical cavity surface emitting laser are stacked in this order, and a second P-type semiconductor layer having a resonator structure of the first and second conductive semiconductor layers is formed in the other region.
Forming an IN-type photodiode, wherein the first PIN
And the second PIN photodiode is formed of the same semiconductor layer.

In a second monolithic light emitting / receiving element according to the present invention, the first PIN photodiode detects an emitted light of the vertical cavity surface emitting laser, and the second PIN photodiode detects the light emitted from the vertical cavity surface emitting laser.
The IN-type photodiode is characterized by detecting external reflected light of light emitted from the vertical cavity surface emitting laser or light from another light emitting element.

The third monolithic light emitting / receiving element of the present invention may further comprise a first conductivity type first light emitting element on the high resistance semiconductor substrate.
A first conductive type first contact layer, an absorption layer, a second conductive type second contact layer, a second conductive type second semiconductor multilayer mirror, A two-conductivity-type first cladding layer, an active layer having a quantum well structure,
A second cladding layer of the first conductivity type, a third semiconductor multilayer mirror of the first conductivity type, and a third contact layer of the first conductivity type are laminated in this order, and the one region is formed of the region Removing the high-resistance semiconductor substrate and the first semiconductor mirror of the first contact layer, the absorption layer, and the second contact layer to form the first PIN photodiode; The second semiconductor multilayer mirror, the first cladding layer, the active layer, the second cladding layer, the third semiconductor multilayer mirror, and the third contact layer have the vertical structure. A cavity surface emitting laser is formed, and the other region includes the first semiconductor multilayer mirror, the first contact layer, the absorption layer, the second contact layer, and the second Resonator structure in part of the semiconductor multilayer mirror It said second PIN photodiode having, characterized in that is formed.

According to a fourth aspect of the present invention, there is provided a monolithic light emitting / receiving element, wherein the first semiconductor multilayer mirror, the first contact layer, the absorbing layer, and the 2 contact layer, the second semiconductor multilayer mirror, the first clad layer, the active layer, the second clad layer, the third contact layer, and the dielectric multilayer mirror Are stacked in this order, and in the one region, the high-resistance semiconductor substrate and the first semiconductor mirror in the region are removed, and the first contact layer, the absorption layer, and the second contact are removed. The first PIN photodiode, the second semiconductor multilayer mirror, the first clad layer, the active layer, the second clad layer, and the third contact layer. And the dielectric multilayer film The vertical cavity surface emitting laser is formed by the first mirror, and the other region includes the first semiconductor multilayer mirror, the first contact layer, the absorption layer, and the second contact layer. And the second PIN photodiode having a resonator structure is formed by a part of the second semiconductor multilayer mirror.

In the fifth monolithic light emitting / receiving device of the present invention, the wavelength at which the vertical cavity surface emitting laser resonates at room temperature is shorter than the wavelength at which the second PIN photodiode resonates at room temperature. So that
The thickness of each semiconductor layer is determined.

According to a sixth monolithic light emitting / receiving element of the present invention, the first contact layer, the second contact layer, and the third contact layer are respectively exposed, and the exposed portions are each provided with a first contact layer. And a second electrode and a third electrode are formed, and in the one region, a current is injected into the vertical cavity surface emitting laser at the second electrode and the third electrode, A current flowing through the first PIN photodiode is detected by a first electrode and a second electrode, and the other region has a resonator structure formed by the first electrode and the second electrode. A current flowing through the second PIN photodiode is detected.

According to a seventh aspect of the present invention, there is provided a monolithic light emitting / receiving element, wherein each semiconductor layer in the one region is electrically insulated from each semiconductor layer in the other region. And

Further, a first optical pickup of the present invention has the monolithic light emitting / receiving element, irradiates a laser beam emitted from the vertical cavity surface emitting laser to an optical disk, and reflects the laser light from the optical disk. Light is received by a second PIN photodiode having a resonator structure, and data is recorded on and reproduced from the optical disk.

In a second optical pickup according to the present invention, a transparent substrate having an objective lens formed on one surface and a diffraction grating formed on the other surface, the monolithic light emitting / receiving element, A surface on which the diffraction grating is formed,
The surface of the monolithic light emitting / receiving element that emits light of the vertical cavity surface emitting laser faces the optical axis of the objective lens on the transparent substrate, and the light emitting portion of the vertical cavity surface emitting laser. It is formed by positioning and bonding so that the center substantially coincides with the center, and mounted on the flying slider.

In a third optical pickup according to the present invention, the objective lens is a blazed grating lens having a sawtooth shape formed on the transparent substrate.

The fourth optical pickup of the present invention is formed by forming a mask having a circular opening on the transparent substrate by the objective lens and then forming a refractive index distribution in the transparent substrate by ion exchange processing. Characterized in that it is a micro flat lens.

According to a fifth optical pickup of the present invention, the monolithic light receiving / emitting element has two light receiving portions composed of the second PIN photodiode, and the diffraction grating is parallel to a recording track of the optical disk. It is divided into two regions by a straight line, and of the reflected light from the optical disc,
Diffracted light by one region of the diffraction grating is incident on the one light receiving portion, and diffracted light by the other region of the diffraction grating is incident on the other light receiving portion, and the difference between the two light receiving portions is obtained. , And the data is reproduced by taking the track error signal by taking the sum of the two light receiving portions.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
This will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a view schematically showing a cross section of a light emitting section and a light receiving section of a monolithic light receiving / emitting element 100 according to an embodiment of the present invention, and FIG. 2 is a schematic perspective view thereof.

In the monolithic light emitting / receiving element 100 shown in FIGS. 1 and 2, a light emitting section 100A and a light receiving section 100B are formed in different regions on a high-resistance semiconductor substrate 101, respectively. In the present embodiment, the light emitting unit 100A includes a vertical cavity surface emitting laser (VCSEL 100A1) and a PIN photodiode 100A2 that monitors the amount of emitted light.
The light receiving sections 100B are each formed of a PIN photodiode having a resonator structure. This light emitting unit 10
As a planar layout of the light receiving unit 100A and the light receiving unit 100B, as shown in FIG. 2, for example, light receiving units 100B are formed at two positions on both sides of the light emitting unit 100A. The numbers of the light emitting portions 100A and the light receiving portions 100B of the monolithic light emitting and receiving element 100 are not limited to the numbers shown in FIG. 2, and a plurality of light emitting portions and a plurality of light receiving portions can be laid out in a plane. is there.

First, the structure of the light emitting section 100A will be described. On the semiconductor substrate 101 made of GaAs, p
A distributed reflection type multi-layer mirror (having a reflectivity of 99.5% or more with respect to light near a wavelength of 780 nm, for example) in which 30 pairs of type Al _0.15 Ga _0.85 As layers and p-type AlAs layers are alternately stacked in this order. First p-type DBR mirror 102), p-type Al _0.15 Ga _0.85 As layer (first p-type contact layer 103), GaAs layer (absorption layer 104), n-type Al
_0.15 Ga _0.85 As layer (n-type contact layer 10
5) is formed. And a single layer of n-type AlA
An s layer is stacked, and n-type Al _0.15 Ga _0.85 A
A distributed-reflection multilayer mirror (n-type DBR mirror 106A) having an reflectivity of 99.5% or more with respect to light near a wavelength of 780 nm is formed by alternately stacking 30 pairs of s layers and n-type AlAs layers in this order. ing. Further thereon, an n-type Al _0.5 Ga _0.5 As layer (n-type clad layer 107), an Al _0.3 Ga _0.7 As barrier layer and a GaAs
An active layer 108 having a multiple quantum well structure composed of s quantum well layers and five quantum well layers, p-type Al _0.5 Ga
_0.5 As layer (p-type cladding layer 109), p-type AlAs
Layers and p-type Al _0.15 Ga _0.85 As layers are laminated alternately in this order in 13 pairs, and 9 layers are formed for light near a wavelength of 780 nm.
Distributed reflection type multilayer mirror having a reflectance of 8.5% to 99% (second p-type DBR mirror 110), p-type Al
_{A 0.15} Ga _0.85 As layer (second p-type contact layer 111) is formed. And the first p-type DBR
The mirror 102 and the semiconductor substrate 101 are provided with a light emitting unit 100A.
Has been removed in the area directly below. Therefore, the light emitting unit 1
Reference numeral 00A denotes an n-type DBR mirror 106A and a VCSEL 100A1 at a portion stacked thereover, and a first p-type contact layer 103, an absorption layer 104, and a n-type contact layer 105 to monitor the amount of light emitted from the VCSEL. The diodes 100A2 are respectively formed. Then, the p-type ohmic electrode 116 and the n-type ohmic electrode 1
A current is injected into the VCSEL 100A1 by 17A.
Further, a current corresponding to the amount of light emitted from the VCSEL from the first p-type DBR mirror 102 is detected by the p-type ohmic electrode 118A and the n-type ohmic electrode 117A. Here, since 100A2 is a PIN photodiode, its response speed is fast, and it can have a sufficient response speed to the light emitted from the VCSEL that has been modulated at high speed.

Here, the active layer 108 has a multi-quantum well structure. By adopting this structure, it is well known that (a) a low threshold current is possible and (b) the width of the quantum well is reduced. The oscillation wavelength can be shortened by making it narrow, (c) the temperature dependence of the threshold current is small,
(D) The high-speed modulation characteristic is excellent. Here, in the above feature (b), the oscillation wavelength determined by the width of the quantum well and lambda _1, n-type cladding layer 107,
Assuming that the resonance wavelength determined by the length of the resonator composed of the active layer 108 and the p-type cladding layer 109 is λ ₂ , λ ₁
And λ ₂ shift to the longer wavelength side as the injection current increases, because the resonator portion of the light emitting unit 100A locally generates heat at the time of current injection, but the shift amount of λ ₁ is shifted by λ ₂ Greater than quantity. Therefore, in order to continuously oscillate the VCSEL, the width of the quantum well must be determined so that λ ₁ at room temperature is shorter than λ ₂ . In the present embodiment, the width of the quantum well and the length of the resonator are determined so as to continuously oscillate at a wavelength near 780 nm.

Here, the first p-type DBR mirror 10
2 was partially removed for the following two reasons. That is, the first reason is that the p-type DBR mirror 102 is
VCSEL to configure an external resonator for SEL
This is to avoid influencing the stable laser oscillation. The second reason is that when the first p-type DBR mirror 102 is located at this portion, the PIN photodiode has a resonator structure sandwiched between the first p-type DBR mirror 102 and the n-type DBR mirror 106A. Become. This P
The cavity length of the IN-type photodiode is designed so as to resonate around the oscillation wavelength (780 nm) of the VCSEL at room temperature, as described later. The temperature becomes higher than room temperature, and the cavity length becomes longer. That is, the reason is that the resonance wavelength due to the resonator structure in this portion shifts to the longer wavelength side and deviates from the wavelength of the light emitted from the VCSEL.

On the other hand, the structure of the light receiving section 100B will be described. A first p-type DBR mirror 102 is formed on a semiconductor substrate 101, and a first p-type contact layer 103 and an absorption layer 104 are further formed thereon. , N-type contact layer 1
Further, an n-type AlAs layer and an n-type Al _0.15 Ga _0.85 As layer are alternately stacked thereon in this order, and have a reflectance of about 82% with respect to light near a wavelength of 780 nm. 5 pairs of distributed reflection type multilayer mirrors (n-type DB
R mirror 106B) is formed. Therefore, the light receiving section 100B forms a PIN photodiode having a resonator structure sandwiched between the first p-type DBR mirror 102 and the n-type DBR mirror 106B. And
P-type ohmic electrode 118B and n-type ohmic electrode 11
7B, the VCS from the second p-type DBR mirror 111
A current corresponding to the amount of reflected light from a measurement object (not shown) in the light emitted from the EL is detected. Here, since the light receiving unit 100B is a PIN photodiode, the response speed is high,
It can have a sufficient response speed to high-speed modulated light.

Here, the light receiving section 100B is
The current flowing is very small as compared with A, and the light emitting unit 100A
, The temperature of the light emitting portion is substantially equal to room temperature even during laser oscillation of the VCSEL 100A1. Therefore, the cavity length of the light receiving section 100B is V at room temperature.
The length was set to resonate with the oscillation wavelength of the CSEL 100A1.

The reason why the number of pairs of the n-type DBR mirror 106B is set to 5 will be described below.

When the light receiving section has a resonator structure, Ap
pl. Phys. 78 (2), 15 July 1995
pp. As shown in 608 to 610, when the quantum efficiency of the light receiving element is represented by the ratio between the amount of light absorbed by the absorption layer and the amount of light incident on the light receiving element, the following equation is obtained.

[0031]

(Equation 1)

Where λ is the wavelength, R ₁ is the reflectance of the n-type DBR mirror 106 B, and R ₂ is the first p-type DBR mirror 1
02, α is the absorption coefficient of the absorption layer 104,
Of p-type contact layer 103, and an absorbing layer 104, the refractive index of the n-type contact layer 105 and a thickness of each _{n 1} and _d 1, _{n 2} and _d 2, _{n 3} and _{d 3.} Also,
Absorption in each layer other than the absorption layer 104 was ignored.

[0033] Here, the λ is the wavelength of the light emitted from the light emitting portion 100A (780 nm in this embodiment) shows the change in quantum efficiency when changing the R ₁ in FIG. In the figure, the solid line indicates the value calculated by the above equation. In addition, the black dots indicate n-type DBRs.
It shows the value of the quantum efficiency when the number of pairs of the mirror 106B is changed, and the number attached to each point is an n-type DBR
This shows the number of pairs of the mirror 106B. From this figure, n-type DB
The number of pairs of the R mirror 106B was set to 5 pairs (R ₁ = 0.82) at which the highest quantum efficiency was obtained. Further, the R ₁ and 0.82 in the above equation indicates when varying the wavelength lambda, the result of calculating the quantum efficiency in FIG. From FIG.
00B has a wavelength band in quantum efficiency. Therefore, since the quantum efficiency of the light receiving unit 100B is reduced for light other than near the wavelength of light emitted from the light emitting unit A, noise due to external light or the like can be reduced.

Hereinafter, the structure and the manufacturing process of the monolithic light emitting / receiving element 100 according to this embodiment will be described with reference to FIGS.

First, a first p-type D
BR mirror 102, first p-type contact layer 103, absorption layer 104, n-type contact layer 105, n-type DBR mirror 106, n-type cladding layer 107, active layer 108, p-type cladding layer 109, second p-type The DBR mirror 110 and the second p-type contact layer 111 are sequentially epitaxially grown by MOCVD (FIG. 5A). At this time, in this embodiment, the growth temperature is 700 ° C., and the growth pressure is 15 ° C.
0 Torr, an organic metal of TMGa (trimethylgallium) and TMAl (trimethylaluminum) as a group III source, AsH ₃ as a group V source, H ₂ Se as an n-type dopant, and DEZn ( Diethyl zinc). Here, the doping amount of the layer to be doped is determined by the respective layers of the first p-type DBR mirror 102, the respective layers of the n-type DBR mirror 106, the n-type cladding layer 107, the p-type cladding layer 109,
Each layer of the second p-type DBR mirror 110 is 2 × 10
¹⁸ (cm ⁻³ ) and the first p-type contact layer 10
3. The n-type contact layer 105 and the second p-type contact layer 111 were 1 × 10 ¹⁹ (cm ⁻³ ). In this embodiment, each layer is epitaxially grown by MOCVD, but may be epitaxially grown by MBE.

Thereafter, a protective layer I1 made of a SiO ₂ layer having a thickness of about 250 Å is formed on the epitaxial layer by a normal pressure thermal CVD method. By covering the semiconductor layer on which the protective layer I1 is laminated, surface contamination during the process is prevented.

Next, a portion of the periphery of the columnar portion 112 which is not covered with the resist pattern R1 is etched halfway through the p-type cladding layer 109 by a reactive ion beam etching method (hereinafter, referred to as a RIBE method). . At this time, in this embodiment, a mixed gas of chlorine and argon is used as an etching gas, and the gas pressure is 1 × 10 ⁻³ Torr,
The extraction voltage was set to 400V. The reason why the etching is performed only in the middle of the p-type cladding layer 109 is that the structure for confining the injected carriers and light in the horizontal direction of the active layer is a rib waveguide type refractive index waveguide structure.
Further, in order to form a current confinement portion 113 for increasing the injection current density near the light emission center of the light emitting portion 100A, a part of the AlAs layer of the second p-type DBR mirror 110 is selectively oxidized (FIG. 5). (B)). This current constriction 1
In order to form 13, one or both of the p-type cladding layer 109 and the second p-type DBR mirror 110 may be insulated by introducing impurities such as protons or oxygen ions by, for example, ion implantation.

Thereafter, the resist pattern R1 is removed, and an SiO ₂ insulating film 114 of about 1000 Å is formed on the surface by normal pressure thermal CVD. As process conditions at this time, a substrate temperature was 450 ° C., SiH ₄ (monosilane) and oxygen were used as raw materials, and nitrogen was used as a carrier gas. Further, an SOG (Spin on Grass) film 115 is applied thereon by using a spin coating method, and thereafter, for example, is applied at 80 ° C. for 1 minute and at 150 ° C. for 2 minutes.
Baking in a nitrogen atmosphere at 300 ° C. for 30 minutes (FIG. 6A).

Next, the SOG film 115 and the SiO ₂ film 114
Is etched back to expose the exposed p-type contact layer 1.
11 was flattened so as to be flush with the surface of FIG.
(B)). A reactive ion etching (RIE) method using a parallel plate electrode was employed for the etching, and SF ₆ , CHF ₃ and Ar were used in combination as a reaction gas.

Next, the light emitting portion 100A is left in a columnar shape, and the periphery thereof and the light receiving portion 100B are divided by an n-type DBR mirror 106 so that the reflectance of the light receiving surface of the light receiving portion 100B becomes optimal for light detection. Etch leaving pair. For this etching, a protective film I2 (for example, SiO ₂ ) is formed, and a resist pattern R2 is formed in a region opposed to the light emitting portion 100A that should not be etched (FIG. 7A).

Next, an n-type ohmic electrode 117A,
B, a light emitting unit 100A and a light receiving unit 100B
Is etched until the surface of the n-type contact layer 105 is exposed. For this etching, after removing the resist pattern R2, the protective film I3 (eg, SiO 2
₂ ) forming the light emitting part 10 which should not be etched
A resist pattern R3 is formed in a region opposed to the light receiving portion 100A and the light receiving portion 100B (FIG. 7B).

Next, the p-type ohmic electrode 118A,
In order to form B, the periphery of the portion where the surface of the n-type contact layer 105 is exposed is etched until the first p-type contact layer 103 is exposed. For this etching, after removing the resist pattern R3, a protective film I4 (for example, SiO ₂ ) is formed, and a region opposing the light emitting unit 100A and the light receiving unit 100B which should not be etched, and the surface of the n-type contact layer 105 A resist pattern R4 is formed in a region opposing the portion where is exposed (FIG. 8A).

Further, the resist pattern R4 is removed,
After forming the protective film I5 (for example, SiO ₂ ), the light emitting unit 1
In order to electrically insulate the first p-type contact layer 103 of the light-receiving unit 100A and the light-receiving unit 100B from the n-type contact layer 105 of the light-emitting unit 100A and the light-receiving unit 100B, the boundary between the two is connected to the semiconductor substrate 101. The separation groove 119 is formed halfway, for example, by etching. It is preferable to use dry etching in forming the separation groove 119, but since the interface in the separation groove 119 does not affect light emission and light reception, it can be formed by wet etching or a dicing saw. Further, instead of the insulation by the separation groove 119, an impurity such as a proton or an oxygen ion may be introduced into the boundary portion by, for example, ion implantation to be insulated.
Further, the first p-type DB of the light emitting section 100A
In order to remove the R mirror 102, a hole 120 was formed by, for example, wet etching (FIG. 8B).

Finally, the protective films I2 to I5 are removed, and the first p-type ohmic electrodes 118A and 118B are exposed at the exposed portion of the first p-type contact layer 103, and the n-type contact layer 105 is exposed. N-type ohmic electrode 117
A, a B, further the second p-type ohmic electrode 116 that contacts the ring-shaped on the exposed portion of the second p-type contact layer 111 was formed by a known lift-off method, alloying of 400 ° C. in a N ₂ atmosphere (FIG. 9).

Through the above steps, the monolithic light emitting / receiving element 100 shown in FIG. 1 is completed.

In the above embodiment, a monolithic light emitting / receiving element having the opposite polarity by exchanging the p type and the n type in each layer does not depart from the gist of the present invention. In the above embodiment, the AlGaAs-based VC is used.
Although the SEL has been described, other III-V or II-VI VCSELs can be suitably applied.
In particular, the active layer can change the oscillation wavelength by changing the composition of Al. In the above embodiment, the second
And the second p-type DBR mirror 110 is omitted.
After the formation of the type ohmic electrode 116, for example, SiO 2
A dielectric multilayer mirror in which _two layers and Ta ₂ O ₅ are alternately stacked may be formed only on the light emitting unit 100A.

Hereinafter, another embodiment in which the above-described monolithic light emitting / receiving element 100 of the present invention is applied to an optical pickup will be described.

Embodiment 2 FIG. 10 is a schematic perspective view showing the structure of an optical pickup 200 according to the present invention.

In the figure, a micro objective lens 202 made of a blazed grating lens having a sawtooth cross section is formed on one surface of a transparent substrate 201 such as glass, and a micro objective lens 202 is formed on the other surface. Diffraction grating 2 divided into two regions by a straight line orthogonal to the optical axis of
03 is formed. Here, the micro objective lens 2
Reference numeral 02 may use, instead of the blazed grating lens, a micro flat lens formed by forming a mask having a circular opening on a transparent substrate and then imparting a refractive index distribution to the transparent substrate by ion exchange treatment.

The optical pickup 200 includes a monolithic light emitting / receiving element 100 formed in a two-dimensional array and a micro objective lens 202 and a transparent substrate 201 formed in a plurality of diffraction gratings 203 in a two-dimensional array. What was attached at a constant interval was cut out for each element. Here, the monolithic light emitting / receiving element 100 and the transparent substrate are, as shown in the figure,
The laser emission side of the monolithic light emitting / receiving element 100 and the diffraction grating 203 face each other.
0 so that the optical axis of the light emitted from the light emitting unit 100A coincides with the optical axis of the micro objective lens 202, and furthermore, the dividing line of the diffraction grating 203 and the monolithic light receiving / emitting element 1
The light-receiving portions 100BR and 100BL above the light-receiving portion 100 are aligned and adhered so as to be substantially parallel to each other. Here, it is easy to form a plurality of monolithic light emitting / receiving elements 100, micro objective lenses 202, and diffraction gratings 203 in a two-dimensional array, respectively, and the position of each element can be positioned with high precision by photolithographic technology. Therefore, a large number of optical pickups 200 can be created at the same time. The conventional optical pickup separately manufactures the individual elements and requires high-precision assembly adjustment, so that miniaturization is difficult and costly, whereas the optical pickup 200 of the present invention is very small. Nevertheless, there is a great merit that it is easy to make a large amount at the same time.

The optical pickup 200 is fixed to a floating slider (not shown).
It floats at a fixed distance from the optical disk 201 so that the micro objective lens 202 always focuses on the recording surface of the optical disk 201. For this reason, the optical pickup 200 of the present embodiment does not need to perform focus servo, and the configuration can be greatly simplified. Further, since the optical pickup 200 is mounted on the flying slider, no disc tilt occurs, and high-accuracy tracking can be performed.

Here, the optical pickup 200 is installed such that the dividing lines of the two regions of the diffraction grating 203 are parallel to the track direction of the optical disk. Then, the area 2 is adjusted so that the diffracted light in the area 203R of the reflected light from the optical disk is almost entirely incident on the light receiving section 100BR.
The shape of the diffraction grating 203 is determined such that almost all the diffracted light at 03L is incident on the light receiving unit 100BL.
In this embodiment, the respective regions of the diffraction grating 203 are blazed to opposite polarities so that the diffracted light in the region 203R is substantially only the + 1st-order diffracted light and the diffracted light in the region 203L is substantially the only −1st-order diffracted light. I have.

Next, the operation of the optical pickup 200 will be described.

First, the light emitting section 10 is driven by the driving circuit 205.
The 0 A VCSEL emits laser light. At this time, V
The PIN of the light emitting unit 100A is determined according to the amount of light emitted from the CSEL.
APC (auto power control) is performed by detecting the current flowing through the photodiode with the IV converter 204 and applying feedback to the drive circuit 205 so that the amount of emitted light is constant.

The laser light emitted from the light emitting section 100A passes through the diffraction grating 203 and is focused on the recording surface of the optical disk by the micro objective lens 202. The reflected light from the optical disk passes through the micro objective lens 202, is diffracted by the diffraction grating 203, is separated by the dividing line, and enters the light receiving unit 100BR and the light receiving unit 100BL.
The amount of current flowing through the light receiving unit 100BR and the light receiving unit 100BL is calculated by an IV converter 206R and an IV converter 206L, respectively.
, And the difference between the respective signals is obtained by the differential amplifier 207, whereby the track error signal (T
ES), and the sum of the respective signals is obtained by the addition amplifier 208 to detect the data signal (RFS).

As described above, by applying the monolithic light receiving / emitting element of the present invention to an optical pickup,
Very small optical pickups can be made in large quantities and easily.

[0057]

The monolithic light-receiving / emitting device of the present invention can be integrated with the light-receiving device and the light-emitting device on the same substrate while ensuring high positional accuracy. Furthermore, the light receiving element is set to PIN
The use of the photodiode makes it possible to improve the response speed to high-speed modulated light. Further, the light receiving portion other than the portion for monitoring the output of the VCSEL of the light emitting portion is a PIN type photodiode having a resonator structure, so that light receiving sensitivity can be improved and noise such as external light can be reduced. can do.

Further, by applying the monolithic light-receiving / emitting element of the present invention to an optical pickup, a small-sized optical pickup that can be easily manufactured can be realized, and the speed of recording and reproduction on an optical disk, the size of the entire apparatus, and the power saving can be reduced. Can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a cross section of a monolithic light emitting and receiving device according to one embodiment of the present invention.

FIG. 2 is a schematic perspective view of the device shown in FIG.

FIG. 3 is a diagram showing how the quantum efficiency changes when R ₁ is changed in equation (1) and when the number of pairs of n-type DBR mirrors 106B is changed in FIG.

FIG. 4 is a diagram illustrating a case where R ₁ is an n-type DBR mirror 10 in equation (1).
When the number of pairs of 6B is five, the reflectance is 5
FIG. 9 is a diagram illustrating a state of a change in quantum efficiency when a wavelength incident on 00B is changed.

FIGS. 5A and 5B are schematic cross-sectional views for explaining a manufacturing process of the device shown in FIG. 1;

FIGS. 6A and 6B are schematic cross-sectional views for explaining a manufacturing process performed subsequently to FIG. 5;

FIGS. 7A and 7B are schematic cross-sectional views for explaining a manufacturing process performed subsequently to FIG. 6;

FIGS. 8A and 8B are schematic cross-sectional views for explaining a manufacturing process performed after FIG. 7;

FIG. 9 is a schematic cross-sectional view for explaining a manufacturing process performed subsequently to FIG. 8;

FIG. 10 is a schematic perspective view schematically showing an optical pickup according to one embodiment of the present invention.

FIG. 11 is a cross-sectional view schematically showing a cross section of a conventional monolithic light emitting / receiving element.

[Explanation of symbols]

100A Light emitting unit 100A1 VCSEL 100A2 PIN photodiode 100B, 100BR, 100BL Light receiving unit 101 High-resistance semiconductor substrate 102 First p-type DBR mirror 103 First p-type contact layer 104 Absorption layer 105 N-type contact layer 106, 106A , 106B n-type DBR mirror 107 n-type cladding layer 108 active layer 109 p-type cladding layer 110 second p-type DBR mirror 111 second p-type contact layer 112 columnar portion 113 current constriction portion 114 SiO ₂ insulating film 115 SOG film 116, 118A, 118B P-type ohmic electrode 117A, 117B N-type ohmic electrode 119 Separation groove 120 Hole I1, I2, I3, I4, I5 Protective film R1, R2, R3, R4 Resist pattern 201 Optical disk 202 Ma Black objective lens 203,203R, 203L grating 204,206R, 206L I-V converter 205 driving circuit 207 differential amplifier 208 summing amplifier

Claims (12)

[Claims] A first conductivity type semiconductor layer and a second conductivity type semiconductor layer, each of which is formed by laminating a plurality of layers in at least two regions on a high resistance semiconductor substrate; A first PIN type photodiode and a vertical cavity surface emitting laser are stacked and formed in this order on the first and second conductive type semiconductor layers, and the first and second conductive type semiconductors are formed in the other region. A second PIN photodiode having a resonator structure is formed in the layer, and the first PIN photodiode and the second PI
A monolithic light emitting / receiving element, wherein an N-type photodiode is formed of the same semiconductor layer. 2. The vertical cavity surface emitting laser according to claim 1, wherein the first PIN photodiode detects emission light of the vertical cavity surface emitting laser, and wherein the second PIN photodiode emits the vertical cavity surface emitting laser. A monolithic light-receiving / emitting element, which detects external reflected light of laser emission light or light from another light-emitting element. 3. The semiconductor device according to claim 1, wherein a first semiconductor multilayer mirror of a first conductivity type, a first contact layer of a first conductivity type, and a first contact layer of the first conductivity type are provided on the high-resistance semiconductor substrate. An absorption layer, a second contact layer of the second conductivity type, a second semiconductor multilayer mirror of the second conductivity type, a first cladding layer of the second conductivity type, an active layer of a quantum well structure, A second cladding layer of the first conductivity type, a third semiconductor multilayer mirror of the first conductivity type, and a third contact layer of the first conductivity type are laminated in this order. Removing the high-resistance semiconductor substrate and the first semiconductor mirror of the first contact layer, the absorption layer, and the second contact layer with the first PIN photodiode; A second semiconductor multilayer mirror, the first cladding layer, and the active layer; The vertical cavity surface emitting laser is formed by a layer, the second cladding layer, the third semiconductor multilayer mirror, and the third contact layer, and the other region includes the first region. A semiconductor multilayer mirror of
The second PIN photodiode having a resonator structure is formed by the first contact layer, the absorption layer, the second contact layer, and a part of the second semiconductor multilayer mirror. A monolithic light emitting / receiving element characterized by: 4. The semiconductor device according to claim 1, wherein the first semiconductor multilayer mirror, the first contact layer, and the absorption layer are formed on the high-resistance semiconductor substrate.
The second contact layer, the second semiconductor multilayer mirror, the first cladding layer, the active layer, the second cladding layer, the third contact layer, and the dielectric multilayer A film mirror is stacked in this order; the one region removes the high-resistance semiconductor substrate and the first semiconductor mirror in the region, the first contact layer, the absorption layer, and the second The first PIN photodiode, the second semiconductor multilayer mirror, the first clad layer, the active layer, the second clad layer, and the third The vertical cavity surface emitting laser is formed by a contact layer and the dielectric multilayer mirror, and the other region includes: the first semiconductor multilayer mirror;
The second PIN photodiode having a resonator structure is formed by the first contact layer, the absorption layer, the second contact layer, and a part of the second semiconductor multilayer mirror. A monolithic light emitting / receiving element characterized by: 5. The wavelength according to claim 1, wherein a wavelength at which the vertical cavity surface emitting laser resonates at room temperature is shorter than a wavelength at which the second PIN photodiode resonates at room temperature. A monolithic light emitting / receiving element, characterized in that the thickness of each semiconductor layer is determined as follows. 6. The method according to claim 3, wherein the first contact layer, the second contact layer, and the third contact layer are respectively exposed, and a first contact layer is formed on each of the exposed portions. Forming an electrode, a second electrode, and a third electrode, and in the one region, injecting a current into the vertical cavity surface emitting laser using the second electrode and the third electrode, A current flowing through the first PIN photodiode is detected by the first electrode and the second electrode, and the other region has a resonator structure formed by the first electrode and the second electrode. A monolithic light emitting / receiving element, wherein a current flowing through a second PIN photodiode is detected. 7. The semiconductor device according to claim 1, wherein each of the semiconductor layers in the one region and each of the semiconductor layers in the other region are electrically insulated from each other. Monolithic light emitting and receiving element. 8. A monolithic light emitting / receiving element according to claim 7, wherein the laser light emitted from the vertical cavity surface emitting laser is applied to an optical disc, and reflected light from the optical disc is used as a resonator structure. An optical pickup, which receives light by a second PIN type photodiode having a function of recording and reproducing data on and from the optical disk. 9. The monolithic light emitting / receiving element according to claim 8, wherein the objective lens is formed on one surface and a diffraction grating is formed on the other surface, and the monolithic light emitting / receiving element is formed on the transparent substrate. The formed surface and the surface of the monolithic light receiving and emitting element that emit the light of the vertical cavity surface emitting laser face each other, the optical axis of the objective lens on the transparent substrate, and the vertical cavity surface An optical pickup characterized by being formed by positioning and bonding so that the center of a light emitting portion of a light emitting laser substantially coincides with the center of the light emitting portion, and mounted on a flying slider. 10. The optical pickup according to claim 9, wherein the objective lens is a blazed grating lens having a sawtooth shape formed on the transparent substrate. 11. The micro flat lens according to claim 9, wherein the objective lens forms a mask having a circular opening on the transparent substrate, and then forms a refractive index distribution in the transparent substrate by an ion exchange process. An optical pickup, characterized in that: 12. The monolithic light emitting and receiving element according to claim 9, wherein the monolithic light emitting and receiving element has two light receiving sections including the second PIN photodiode, and the diffraction grating is parallel to a recording track of the optical disc. Of the reflected light from the optical disc, the diffracted light by one area of the diffraction grating is incident on the one light receiving portion, and is diffracted by the other area of the diffraction grating. Light incident on the other light receiving unit, and a track error signal is obtained by taking a difference between the two light receiving units, and the data is reproduced by taking a sum of the two light receiving units. pick up.