JPS604278A - Light emitting diode - Google Patents

Abstract

PURPOSE:To obtain the titled device which enables high speed response by reducing the P-N junction capacitance parasitic in the periphery while preventing the formation of the remote junction in the light emitting part. CONSTITUTION:The device is composed of the first buffer layer 2 epitaxially grown on a semiconductor substrate 1, the second buffer layer 3, an active layer 4, a clad layer 5, an electrode forming layer 6, a current stricture layer 7 including a current injected part 71, and N-side electrode 8 including a light lead-out window 81, a P-side electrode 9, and a Zn diffused region 10. Besides, it acts as a surface light emitting type light emitting diode which takes out light emission from the window 81 by the stricture and injection of current from the part 71 to the layer 4. When the impurity concentration of the second buffer layer 3 is increased in order to prevent the formation of the remote junction in the light emitting part due to Zn diffusion during manufacturing processes, the marked deterioration of the time for response rise in pulse modulation is caused. Therefore, this invention contrives to reduce the P-N junction capacitance parasitic in the periphery due to the transfer of the position of the peripheral P-N junction into the first buffer layer 2 of a low impurity concentration provided under the third buffer layer 3 by peripheral Zn diffusion.

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 drawback of low output, they have features that semiconductor lasers do not have, such as high reliability, high stability in temperature/temperature characteristics, and resistance to reflection noise as a non-coherent light source, so they are used in short- and medium-distance optical transmission. It is a practical element. In particular, high-speed modulation type 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 for 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, many of the impurities used as dopants in the active layer are easily diffused during the device manufacturing process, so in the conventional device structure, the impurity 'l/J' of the active layer is
Even if the temperature is increased by 713"8 degrees, a remote junction is formed which causes a significant decrease in optical output and response speed, resulting in the disadvantage that necessary device characteristics cannot be obtained.

On the other hand, in order to prevent the formation of remote junctions, it is good to increase the impurity concentration of the buffer layer, which has a conductivity type opposite to that of the active layer. The parasitic p-n junction capacitance caused by the peripheral crut Jl''7 expansion through the cylindrical resistor increases significantly, resulting in a disadvantage that high-speed response cannot be obtained.

The purpose of FUJI J is to eliminate the above-mentioned drawbacks and to provide a purple light emitting diode that is capable of high-speed modulation and is easy to manufacture.

According to the present invention, - a first buffer layer having the same conductivity type as the semiconductor substrate on a semiconductor substrate having a conductivity type, a second buffer layer having the same conductivity type as the semiconductor substrate;
An active layer, a cladding layer having a conductivity type opposite to that of the semi-quaternary substrate, and a current narrow q layer including a current injection part are formed, and the impurity concentration of the second Balanor layer in iIJ is equal to the second The impurity content of the buffer layer is extremely low, and the impurity of the conductivity type opposite to that of the semiconductor substrate is diffused into the active layer and the second buffer layer located around the current conductive part. A light emitting diode is obtained.

The details will be briefly explained below with reference to the drawings. The drawing shows a cross section of an embodiment according to the invention. In this embodiment, a first buffer layer 2, a second buffer layer 3, an active layer 4, which are epitaxially grown on a semiconductor substrate 1,
The cladding layer 5, the electrode formation M6, and the current injection part 71 are included in the cladding layer 5, the narrow 9M7, and the light extraction window 81 is included.
111 t44 = s, p 1u1j electrode 9, Zn[consisting of region 10]. Half u! One board 1 is (1
00) orientation, made of InP doped with 1×10 c′M Sn, 100 μm thick; the first buffer layer 2 made of InP doped with 1×10 M Sn, 2 μm thick; Second buffer 76'! 3 has Sn of 2
The active layer 4 is made of doped InP and has a thickness of 1/7771°.
s-' doped I n U4Ga 1126 As
The cladding layer 5 is made of InP doped with Zn and has a thickness of 0.5 μm. I n [184Ga
11+ 6As astr Made from Pn64 Thickness 1I
Jr. The current confinement layer 7 is made of Sin and has a thickness of 0.2P1n, and the n-side electrode 8 is made of an Au-Ge-Ni alloy and has a thickness of 0.3pm+pi! :The electrode 9 is made of Au.
- It is made of Zn alloy and has a thickness of 03 μm. Current narrow -'f
The current injection part 71 with a diameter of 20 .mu.m in the j. In this example, a Znn diffusion region 1o is provided at a depth of about 35 μm from the surface of the electrode forming layer 6 in a region with a radius of 20 μm or more from the center of the current injection part 71. In its operation, diameter 2
Current injection into the active layer 4 is constricted by the current injection part 71 of 0 μm.
It operates as a surface-emitting type light emitting diode that extracts light from the injected light extraction window 81. The impurity concentration of the second buffer layer 3 is sufficient to prevent formation of a remote junction in the light emitting part due to Zn diffusion during the manufacturing process of the active layer 4.

In high-speed pulse modulation of a surface-emitting light emitting diode, if the parasitic admittance value in the peripheral area is not sufficiently small compared to the admittance value of the light emitting part, and its time constant is not sufficiently small compared to the modulation pulse period, This results in significant deterioration of pulse response characteristics. For example, when the size of the device is 300 pm square, in the device of the conventional structure without the first buffer layer 2 and the Zn diffusion region 10 in the example, the expansion resistance of the electrode formation layer, cladding layer, and active layer is small. is 29Ω, and the surrounding pn junction capacitance is 490PF. On the other hand, the operating impedance of the light emitting part is the same forward current of 1
26 Ω at mA, and the time constant of parasitic admittance is 14 ns, which causes a significant deterioration of the response rise time during pulse modulation, and the modulation speed is 50 Ω.
Mb/s lit degree is the limit. This response deterioration is caused by increasing the impurity concentration of the second buffer layer in order to prevent the formation of remote junctions in the light emitting part. of Zn
The purpose is to reduce the parasitic pn junction capacitance around the impurity by moving the impurity into the first buffer layer, which is provided under the second buffer layer and has a low impurity concentration, by diffusion. That is, in the structure shown in the example, the expansion resistance is 2.
0Ω, the peripheral parasitic capacitance is 110PF, the value of the parasitic admittance in the high frequency range is reduced, and the time constant is also shortened to 2.2 ns. Therefore, there is only a slight deterioration in the response rise time during pulse modulation, and 1
A surface-emitting light emitting diode capable of high-speed modulation up to about 50 Mb/s can be obtained.

Note that the semiconductor material and composition need not be limited to the above-mentioned embodiments, and can be applied to IN-V group compound semiconductors of any composition. Doping substances, diffusion impurities, current narrow T
By layer material or n-side electrode material, p 1111'm,
The pole materials also need not be limited to the above-mentioned examples. In particular, the current confinement layer material is not limited to an insulating film, but may be a semiconductor layer. Further, the flow stop constriction structure is not limited to the 414 structure shown in this embodiment, but any structure such as a reverse biased pn junction can be applied. It is also applicable to edge-emitting light emitting diodes. Furthermore, the values of the impurity concentration in each layer thickness, the diameter of the current injection part, the diameter of the light extraction 'g surface, and the position and depth of the Zn diffusion region may take any values.

Finally, to summarize the features of the present invention, the peripheral p
By moving the position of the n-junction into the first buffer layer (sofa layer) with a low impurity concentration provided under the second buffer layer with a high impurity concentration by impurity diffusion in the peripheral region, It is possible to obtain a light-emitting diode capable of high-speed response, which reduces parasitic 21-mode capacitance around the periphery while preventing remote junction formation.

[Brief explanation of drawings]

The figure is a sectional view of one embodiment of the present invention. In the figure, 1 is a semiconductor substrate, 2 is a first buffer layer, 3 is a second buffer layer, 4 is an active layer, 5 is a cladding layer, 6 is an electrode formation layer, 7 is a current narrowing layer 7, 71 is a current 8 is an n-side electrode, 81 is a light extraction window, 9 is a P-side electrode, and 10 is a Zn diffusion region. In-Yu-J1 Ri-ri 1-[Current Stem/

Claims (1)

[Claims] A first buffer layer having the same conductivity type as the semiconductor substrate on a semiconductor substrate having a conductive cage type, a second buffer layer having the same conductivity type as the semiconductor substrate, an active layer, and a conductivity type opposite to the semiconductor substrate. a current confinement layer including a cladding layer and a current injection part, the impurity concentration of the first buffer layer is lower than the impurity concentration of the second buffer layer, and the active current injection part is located around the current injection part. A light emitting diode, wherein an impurity having a conductivity type opposite to that of the semiconductor substrate is introduced into the layer and the second buffer layer.