JPS604277A - Light emitting diode - Google Patents

Abstract

PURPOSE:To enable high speed modulation by the reduction of parasitic capacitance by a method wherein a semiconductor buffer layer doped with an impurity of reverse conductivity type of the degree of compensation of the impurity diffused from an active layer in manufacturing processes is interposed between the active layer of a high impurity concentration and a semiconductor substrate. CONSTITUTION:The titled device is composed of the semiconductor buffer layer epitaxially grown on the substrate 1, the active layer 3, a clad layer 4, an electrode forming layer 5 including a Zn diffused region 51, an N-side electrode 6 including a light lead-out window 62, and a P-side electrode 7. Besides, it acts as a surface light emitting type light emitting diode which takes out light emission from the window 61 by the stricture and injection of current into the layer 3 from the diffused region 51 during action thereof. Further, the parasitic capacitance is reduced and thus the response characteristic is improved by the imposal of the buffer layer 2, whose thickness after the impurity of reverse conductivity type of the degree of compensation of the impurity diffused from the active layer is doped is the half of a carrier diffused length or less, between the substrate 1 of a high impurity concentration and the active layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in light emitting diodes suitable for use in fiber optic communications.

Although light emitting diodes have the disadvantage of low output,
It is a device that is being put into practical use in short- and medium-distance optical transmission because it has features such as high reliability, high temperature stability, and low cost. In particular, high-speed modulation devices that shorten the lifetime of carriers injected into the active layer and improve response speed are expected to have a wide range of applications.

Doping impurities at a high concentration is effective in shortening the lifetime of carriers injected into the active layer, and this method has conventionally been used to increase the response speed of light emitting diodes. However, in the conventional device structure, even if the impurity concentration of the active layer is increased, the parasitic pn junction capacitance around the light emitting part increases, and the response speed is affected by the time constant of the parasitic admittance rather than the lifetime of the carriers injected into the active layer. This has the disadvantage that, as a result, high-speed response characteristics cannot be obtained. On the other hand, in order to reduce the pn junction capacitance, it may be possible to lower the impurity concentration in the semiconductor substrate of the opposite conductivity type to the active layer, but impurities used as dopants in the active layer tend to diffuse during the device manufacturing process. Because of the large number of ions, the pn junction often migrates into the semiconductor substrate, forming a remote junction. In order to suppress the decrease in optical output and response speed due to remote bonding, the junction position 11 (() must be within 1/2 of the carrier diffusion length, but the position of the remote bond should be determined in each step of device manufacturing. It is impossible to reduce the impurity concentration of the semiconductor substrate in order to increase the manufacturing yield because it depends on the
In the end, it had the disadvantage that high-speed response characteristics could not be obtained.

SUMMARY OF THE INVENTION The object of the present invention is to eliminate the above-mentioned drawbacks and to provide a light emitting diode that can be modulated at high speed and is easy to manufacture.

According to the present invention, a semi-conductor containing 11L-type impurities can be obtained.
A semiconductor buffer layer and a semiconductor active layer including an impurity of a second conductivity type opposite to the first conductivity type are formed on the semiconductor buffer layer and the semiconductor buffer layer also has a small bandgap, and the semiconductor buffer layer is the first conductivity type. The first conductivity type impurity and the second conductivity type impurity (71'
The concentration of impurities of the second conductivity type contained in the semiconductor substrate and the concentration of the second conductivity type impurity contained in the semiconductor active layer are respectively
There is obtained a light emitting diode characterized in that the concentration of the impurity of the electric type is lower than the concentration of the impurity, and the layer thickness of the semi-quadramid buffer layer is thinner than 1/2 of the carrier diffusion length.

Next, the present invention will be explained with reference to the drawings. The drawing shows a cross section of an embodiment based on this embodiment. In this embodiment, a semiconductor buffer layer 2, an active layer 3, a cladding layer 4, and a Zn diffusion region 5 are epitaxially grown on a semiconductor substrate 1.
1 and n111 including the light extraction window 61.
11 electrodes 6 and Pflll electrodes 7. The semiconductor substrate 1 has a (100) orientation, and Sn is 3X101
The semiconductor buffer layer 2 is made of doped InP with a thickness of 100p, Sn is 1.5Xi 018an-', and Zn is IX
1018Cffi-' is made from 2x1O18G3 doped InP and has a thickness of 0 μm.

The active layer 3 is made of In0.74GaO,26AsO,56PO4 doped with 7 x 1o18 tmJ of Zn.
The cladding layer 4 has a thickness of 0.5 pm, and the Zn is I.
The electrode forming layer 5 is made of InP doped with X 1018an-' and has a thickness of 1 pm.
n-'dogged I n (L84 Ga a16A
s [Made from 136Po64 and has a thickness of 111 m. The impurity Sn doped into the semiconductor buffer layer 2 was doped during the epitaxial growth of the buffer layer 2, and the impurity Zn was added to the active) 143 during the device manufacturing process after the epitaxial growth of the active layer 3. The buffer layer 2 is doped with Zn which is doped with Zn and diffuses into the buffer layer 2. n 911 electrode 6 is A u -G e
- Ni alloy formed thickness 0.3 pm, P 1
The Illll electrode 7 is made of Au-Zn alloy and has a thickness of 0.3μ.
It is 2n. The Zn diffusion region 51 has a diameter of 20 μm, and the n-side electrode 6 has a light extraction window 6 with a diameter of 120 μm.
1 has been removed by chemical etching. During operation, this embodiment operates as a surface-emitting type light emitting diode in which a current is narrowly injected into the active layer 3 through the region 51 of the Zn expansion 11 having a diameter of 20 μnl, and the light is extracted from the light extraction window 61.

In high-speed pulse modulation of a surface-emitting type light emitting diode, if the parasitic p-to-junction capacitance around the light emitting part is not sufficiently smaller than the diffusion capacitance of the light emitting part, the pulse response characteristics will be significantly deteriorated. For example, when the size of the device is 300 pm square, in the conventional implanted device without the semiconductor buffer layer 2 in the example, the impurity Zn in the active layer diffuses into the semiconductor substrate, and the impurity carrier concentration is compensated for. Even taking this into account, the parasitic capacitance is 490PF at maximum. On the other hand, since the diffusion capacitance of the light emitting part is about 1000 PF, the response speed deteriorates depending on the amount of orange juice, and high-speed modulation of 100 Mb/s or more is difficult. The present invention involves sandwiching a semiconductor buffer layer between a semiconductor substrate with a high impurity concentration and an active layer, doped with an opposite quaternary type impurity to compensate for impurities diffused from the active layer, and having a thickness equal to or less than the carrier diffusion length V2. Yoshi,
This reduces parasitic capacitance and improves response characteristics. That is, in this example, the parasitic capacitance is halved to a maximum of 250PF, and even if the conductivity type of the semiconductor buffer layer is reversed, the layer thickness is sufficiently small compared to the carrier diffusion length, so there is no characteristic deterioration due to remote junction. Response characteristics are revised.

Therefore, a surface-emitting light emitting diode capable of high-speed modulation up to about 200 Mb/s can be obtained.

It should be noted that the material and composition of the present invention are not limited to the above-mentioned embodiments, and can be applied to other group V compound semiconductors of any composition. The impurity electrode material also does not need to be limited to the above embodiments. Further, the current narrow f structure is not limited to the structure shown in this embodiment, and any structure can be applied, and it can also be applied to an edge-emitting light emitting diode. Furthermore, each layer thickness and impurity concentration.

The values of the current injection part it diameter and the light extraction window diameter can be any number 1.
You can also take +i.

Finally, to summarize the features of the present invention, the carrier layer is doped with an opposite conductivity type impurity to compensate for the impurities diffused from the active layer during the manufacturing process between the active layer with a high impurity concentration and the semiconductor substrate. By sandwiching a semiconductor buffer layer with a length of 1/2 or less of the diffusion length, parasitic capacitance can be reduced and a light emitting diode bottom can be obtained that enables high-speed modulation.

[Brief explanation of the drawing]

The figure is a sectional view of one embodiment of the present invention. In the figure, 1 is a semiconductor substrate, 2 is a semiconductor buffer layer, 3 is an active layer, 4 is a cladding layer, 5 is an electrode formation layer, 51 is a Zn diffusion region, and 6 is an n
A side electrode, 61 is a light extraction window, and 7 is a P side electrode. Representative patent attorney extension sound

Claims (1)

[Claims] On a semiconductor substrate containing impurities of a first conductivity type, a semiconductor buffer layer; is configured, the semiconductor buffer layer contains both a first conductivity type impurity and a second conductivity type impurity, and the first conductivity type impurity and the second conductivity type impurity are contained in the semiconductor buffer layer. a layer of the half-barrel buffer layer whose concentration is lower than the concentration of the first conductivity type impurity contained in the semiconductor substrate and the concentration of the second conductivity type impurity contained in the semiconductor active layer, respectively; A light emitting diode characterized in that its thickness is less than 1/2 of the carrier diffusion length.