JPH01215081A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To increase a maximum light output by forming, between one clad layer and a current contraction layer, a semiconductor layer which is of an opposite conductivity type to that of a clad layer. CONSTITUTION:In a double-hetero structure in which the top and bottom surfaces of an active layer 2 are connected to clad layers 1 and 3 respectively, a p-InP layer 7 is formed between the n-InP clad layer 1 and an SI-InP current constricting layer 6. Leak current and an input capacitance of the SI-InP current constricting layer 6 are made small as usual. In the p-InP layer 7, electrons from the n-clad layer 1 are recombined inside to keep the electrons from being injected to the current constricting layer 6. Therefore, carries injected to SI-InP which forms the current constricting layer 6 are only holes from the p-clad layer 3. And, the input current required to take insulation from the current constricting layer 6 gets remarkably larger than usual. By this method, this semiconductor light emitting device increases its maximum light output, keeping the leak current and the input capacitance small.

Description

[Detailed Description of the Invention] [Summary] The upper and lower surfaces of the active layer are respectively bonded to the cladding layer, and the active layer has a double heterostructure, and a semi-insulating semiconductor current confinement layer that fills both sides of the double heterostructure. A semiconductor light emitting device is configured such that a semiconductor layer of a conductivity type opposite to that of the craft layer is interposed between one cladding layer and a current confinement layer for the purpose of improving maximum light output.

[Industrial application field]

The present invention relates to a semiconductor light emitting device having a double heterostructure in which the upper and lower surfaces of an active layer are respectively bonded to cladding layers, and a semi-insulating semiconductor current confinement layer filling both sides of the double heterostructure.

The semiconductor light emitting device described above emits laser light and is used, for example, as an optical signal source for optical communications.As described below, although it has improved characteristics, the maximum optical output is low and the maximum optical output is low. Improvement is desired.

[Conventional technology]

FIG. 2 is a side sectional view of the main part of a conventional semiconductor light emitting device.

In FIG. 2, 1 is an n-1nP cladding layer, 2 is an I
An active layer of nGaAs P, 3 a p, -1nP ground layer, 4 a p"-1nGaAs P contact layer, and 5 a current confinement layer consisting of a p-InP layer 5a and an n-1nPIii 5b.

The active layer 2 has a width of about 1 to 2 μ- and is bonded to the cladding layer 1 and the cladding layer 3 to form a double heterostructure, and the current confinement layer 5 has a pn junction 5c formed by InPM 5a and 5b. , filling a large area on both sides of the double heterostructure.

In this semiconductor light emitting device, when current is passed from the contact layer 4 side to the cladding layer 1 side, most of the current is concentrated in the active layer 2 due to the existence of the pn junction 5c in the opposite direction and emits light, and the current becomes a value ( I th : oscillation threshold current) When the current is increased, laser oscillation occurs and laser light is emitted.

However, the p-cladding layer 3 and the p-1nP layer 5a
Since some of the layers are connected to each other, there is a leakage current flowing from the p-cladding layer 3 to the n-cladding layer l through the p-1nP layer 5a. In this case, the forward direction diode formed by the active layer 3 is DI, the resistance by the p-1nP layer 5a is R, the forward direction diode formed by the p-1nP layer 5a and the n-Craft layer 1 is D2, Although the rising voltage of the diode D2 is larger than that of the diode D1, the leakage current is quite large. This leakage current becomes a problem in that it increases 1th and reduces η (oscillation efficiency).

In addition, the current confinement layer 5 occupies a wide area within the entire surface of the chip.
Since there is a capacitance formed by the pn junction, the input capacitance is as high as 10 to 100 pF for a chip of approximately 300 μ-square, which poses a problem when attempting to operate at high speed.

FIG. 4 is a sectional side view of a main part of a conventional example of a semiconductor light emitting device that has been improved to reduce the leakage current and input capacitance described above.

In the conventional example shown in FIG. 4, the current confinement layer 5 of the semiconductor light emitting device described in FIG.
) The current confinement layer 6 has a single layer structure. This S
1-InP is generally made semi-insulating by introducing impurities such as Fe. Therefore, there is no pn junction in the current confinement layer 6, and the n
- It has a pin structure up to the cladding film.

As a result, both the leakage current and the input capacitance mentioned above become small, I''th is small, η is large, and high-speed operation is possible.

[Problem to be solved by the invention]

However, in this conventional example, the current confinement N6 is formed by
-In Semi-insulating semiconductors such as P are not perfect insulators and usually maintain their insulating properties by capturing residual electrons (or holes) through deep electron (or hole) traps in the crystal. Therefore, as the electric field applied here increases and the injection of carriers increases, it rapidly loses its insulating properties. In particular, when both electrons and carriers of the genuine tag are injected at the same time as in the pin structure, t
Because recombination of carriers in l occurs, the insulating property is lost in a much smaller electric field than in the case of only a single carrier.

Therefore, although the above-mentioned conventional example exhibits good characteristics when the input current is small, when the input current becomes large, η rapidly decreases, and there is a problem that a large maximum optical output cannot be obtained.

Therefore, an object of the present invention is to improve the maximum optical output while ensuring the characteristics of the conventional example of small leakage current and small input capacitance.

[Means to solve the problem]

The above purpose is to have a double heterostructure in which the upper and lower surfaces of the active layer are respectively bonded to cladding layers, and a semi-insulating semiconductor current confinement layer that fills both sides of the double heterostructure, with one cladding layer This is achieved by the semiconductor light emitting device of the present invention in which a semiconductor layer of a conductivity type opposite to that of the cladding layer is interposed between the current confinement layer and the current confinement layer.

[For production]

In the conventional example, the current confinement layer is made of a semi-insulating semiconductor to reduce leakage current and input capacitance, but both electron and hole carriers are simultaneously injected into this semi-insulating semiconductor, keeping the maximum optical output low. It was done.

On the other hand, in the semiconductor light emitting device of the present invention, the current confinement layer is made of a semi-insulating semiconductor to reduce leakage current and input capacitance as in the conventional example, and in addition, the above-mentioned intervening semiconductor layer is provided.

This semiconductor layer internally recombines carriers from the cladding layer with which it is in contact, and prevents the carriers from being injected into the semi-insulating semiconductor, which is the current confinement layer. Therefore, in this semi-insulating semiconductor, only a single carrier is injected, and the magnitude of the electric field at which insulation is lost is greater than in the conventional case where both carriers are injected simultaneously.

Therefore, this semiconductor light emitting device maintains the small leakage current and small input capacitance, which are the characteristics of the conventional example, and improves the maximum light output.

〔Example〕

The following is a first example of the semiconductor light emitting device according to the present invention.
This will be explained using a side sectional view of the main part in the figure. The same reference numerals indicate the same objects throughout the figures.

The embodiment shown in FIG. 1 differs from the conventional example shown in FIG. It is something that

That is, the cladding layer 1 contains Sn at l×IQ”/c
The n-1nPs active layer 2 doped to about d is undoped InGaAs with a bandgap wavelength of, for example, 1.3μ and a thickness of about 0.15μ.
P-1n with a thickness of approximately 2 μ- doped to the extent of XIO”/aJ
Ps contact) N4 is lattice matched to lnP and Zn is lxl
0'U/- doped p"- with a thickness of about 0.5μ
1nGaAsP, and each of these layers has nGaAsP (not shown).
- After being sequentially grown on a 1nP substrate, mesa-etching is performed using a 5iOz stripe film as a mask to form a mesa-stripe structure with a width of about 1 to 2 μm, and the active layer 2 and the bonded to it are mesa-etched. The cladding layer l and the cladding layer 3 have a double heterostructure.

In the conventional example, 51-InP is embedded and grown to form current confinement layers 6 on both sides of the mesa stripe structure, but in the embodiment, p-type impurities such as Zn are diffused from the surface prior to the growth. Then, the surface region of the cladding layer l is coated with an impurity concentration of about 10'e to 10Is/ali and a thickness of 0.2
A p-lnP layer 7 having a thickness of about 1 μ is formed, and then a current confinement layer 6 is formed in the same manner as in the conventional example.

The Sr-In P current confinement layer 6 reduces leakage current and input capacitance as in the conventional example.

The p-lnP layer 7 internally recombines electrons from the n-cladding layer l and prevents the electrons from being injected into the current confinement layer 6. Therefore, the SI forming the current confinement layer 6
- Summer The carriers injected into the nP are only holes from the p- cladding layer 3, and the input current until the current confinement layer 6 loses its insulation properties becomes warmer and larger than in the conventional example.

Thus, this semiconductor light emitting device maintains the small leakage current and small input capacitance, which are the characteristics of the conventional example, and improves the maximum light output.

According to the inventor's confirmation, in the conventional example, the maximum light output is 8m.
Whereas it was saturated with W, in the example it was possible to obtain a light output of 301 m- or more, and 1th and l were both <15- and 0.28a+W/gtA, which were the same. Furthermore, no difference was observed in input capacity.

Instead of p-type impurity diffusion to form the p-lnP layer 7 in the above embodiment, an n-lnP layer may be formed in the surface region of the p-craft layer 3 by diffusing an n-type impurity such as S. In this case, holes from the p-cladding layer 3 are prevented from being injected into the current confinement layer 6, and results similar to those of the embodiment are obtained.

Further, the conductivity type of each layer in the embodiment may be reversed from that in the embodiment.

Furthermore, although the semiconductor light emitting device of the embodiment is an lnP type, the semiconductor light emitting device of the present invention is based on the lnP type based on its principle.
It is not limited to P-type.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, there is a double heterostructure in which the upper and lower surfaces of the active layer are respectively bonded to the cladding layer, and a current confinement layer made of a semi-insulating semiconductor that fills both sides of the double heterostructure. It is possible to improve the maximum optical output while ensuring the characteristics of small leakage current and small power capacity in a semiconductor light emitting device with a small 1th, large η, high speed operation, and high optical output. This has the effect of making it possible to provide equipment.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of the main part of the embodiment, Fig. 2 is a side sectional view of the main part of a conventional semiconductor light emitting device, Fig. 3 is a circuit diagram showing the leakage current of the light emitting device of Fig. 2, and Fig. 4 is This is a side sectional view of the main part of the conventional example. In the figure, 1 is an n-1nP cladding layer, 2 is an InGaAs P active layer, 3 is a p-rnP cladding layer, 4 is a p-1nGaAsP contact layer, and 5 is a p-1
A current confinement layer composed of an nP layer 5a and an n-1nP layer 5b, 6 is an Sl-InP current confinement layer, 7 is a p-1nP layer interposed according to the present invention, Dl is a diode formed by the part 3, and D2 is 5a and 1 form a diode, and R is the resistance due to 5a. Oshiba Kama 0 moves 44 unfilled thorns! 4-rule lamp diagram No. zn 2nd D I and I V leakage electric current B circuit diagram No. 3m Conventional example side 1 view No. 4m

Claims (1)

[Claims] It has a double heterostructure in which the upper and lower surfaces of the active layer are respectively bonded to cladding layers, and current confinement layers made of semi-insulating semiconductor that fill both sides of the double heterostructure, and one of the cladding layers and the current confinement layer. A semiconductor light emitting device characterized in that a semiconductor layer of a conductivity type opposite to that of the cladding layer is interposed therebetween.