JPH02203584A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To prevent the deterioration of oscillation spectrum and improve characteristics by arranging a plurality of electrode isolation trenches, making the bottom parts thereof reach current blocking layers, and electrically isolating electrodes. CONSTITUTION:Electrode isolation trenches 10 are dug up to current blocking layers 6, 7, in the manner in which the distance between the rough of the trench and an active layer 1 becomes (d). Hence, the isolation resistance between electrodes becomes nearly equal to material resistance of a clad layer 3 of the following dimension; the depth is (d), the width is nearly equal to the width of a light emitting region, and the length is equal to the width of the trench 10. As a result, high resistance is easily realized. When the trench width is small, the length of a region in which the current of an active layer 1 is not injected can be neglected, and current-optical output characteristics of the device do not change. Thereby, P-side electrodes 9 can be isolated by the trench 10 without deteriorating distributed feedback type semiconductor laser, and oscillation wavelength is changed by making nonuniform current flow in the active layer 1. Further, a modulation signal can be applied to one of the P-side electrodes 9, and stable modulation characteristics are obtained, so that characteristics of the device are improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to semiconductor light-emitting devices such as semiconductor lasers and light-emitting diodes that can spatially non-uniformly inject current into a light-emitting layer from one electrode. .

[Prior art]

A conventional semiconductor light-emitting device, for example, an Ir1GaAsP/InP-based distributed feedback semiconductor laser as shown in FIG. 4 (a portion of which is removed so that the inside of the device can be described) has been disclosed (Nakano et al. By.

Electronics Letters Volume 23 No. 16 826-828
Page, 1987).

That is, in the distributed feedback semiconductor laser, voltage is applied to the positive and negative n# electrodes 8 and the p-side electrode 9, and the InGaA
By passing a current (injecting electrons and holes) into the active layer (light-emitting layer) 1 made of sP, it emits light, and the light outputs 11 and 1
1' is taken out.

Generally, in order to improve the efficiency of a semiconductor light emitting device and to efficiently confine injected carriers and emitted light to a light emitting region, the band gap is larger than that of the active layer (light emitting layer) 1, and the refractive index is lower than that of the active layer (light emitting layer) 1. A small so-called P-type InP cladding layer 3 and an n-type Dingguo P substrate (n-type InP cladding layer)
5 sandwich the light emitting layer. InGa
The guide layer 2 made of AsP is a layer in which a diffraction grating is formed, and a distributed feedback (reflection) function is introduced into this diffraction grating. Among these positive and negative electrodes, active WJ1
By separating the electrode closer to the active layer 1 into several parts with an electrode separation groove 10 and injecting current into these electrodes independently, the injected carrier density of the active layer 1 can be changed, and the refractive index of the active region can be partially changed. By changing the wavelength, the oscillation wavelength can be made variable. Furthermore, direct modulation and frequency modulation of these semiconductor light emitting devices can be performed independently.

Normally, if the electrodes are not separated, these modulations cannot be performed independently, which poses a problem when applying these optical semiconductor devices to light sources in optical communication systems.

In the figure, 6 and 7 are current blocking layers for efficiently injecting current into the active region (confining current only to the active region), for example, current block N made of p-type InP.
A pn junction between the current blocking layer 7 and the current blocking layer 7 made of n-type InP blocks current flow to this region. Also,
The p-type InGaAsP cap 4 is for ohmic contact of the p-side electrode 9, and 5 is an n-type InP substrate.

As mentioned above, various advantages can be introduced by electrically isolating at least one electrode of a semiconductor light emitting device.

[Problem to be solved by the invention]

However, in the conventional distributed feedback semiconductor laser, it is the electrode separation grooves in the electrode portion that determine the above-mentioned characteristics.
0, and the characteristics of the device are influenced by the quality of the electrode separation groove 10. For example, if the electrode separation groove 10 is stopped by the cap layer 4 on the top of the cladding 3, the groove width of the electrode separation groove 10 is set to 20 μm in order to ensure separation resistance between the electrodes.
It is necessary to do more than that. However, if the area into which current is not injected is made larger than several tens of micrometers, the area into which current is not injected into the active layer 1 expands, absorbing light emitted from the current injecting portion, and degrading the characteristics of the device. Further, if the groove width of the electrode separation groove 10 is narrow and sufficient electrical isolation cannot be achieved, it is extremely difficult to obtain sufficient characteristics, for example, a wavelength variable range of 1 nm or more.

Furthermore, if the electrode separation groove 10 is made too deep for the purpose of increasing resistance, the light emitted from the active layer 1 will be affected by the electrode separation groove 10, and the light will be guided along the active layer 1 like a semiconductor laser. In the undulating structure, a reflecting mirror is equivalently built into the electrode separation groove 10, resulting in a problem that the oscillation spectrum deteriorates.

The present invention has been made to solve the above problems.

SUMMARY OF THE INVENTION An object of the present invention is to provide a separated-electrode semiconductor light-emitting device with good characteristics in which the single oscillation spectrum does not deteriorate.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

In order to achieve the above object, the present invention provides that at least one of the positive and negative electrodes is separated by a physical separation groove.
an electrode separated into two or more, an active layer where light emission occurs,
In a semiconductor light emitting device equipped with a current blocking layer made of p-type and n-type semiconductors for confining current to a light emitting region, it is most important that the bottom of the electrode separation groove reaches the current blocking layer. The characteristics are as follows.

[For production]

According to the above-mentioned means, since the bottom of the electrode separation groove reaches the current block calendar, it is possible to sufficiently electrically isolate the electrodes, so that an electrode with good characteristics that does not deteriorate the oscillation spectrum can be obtained. A separate semiconductor light emitting device can be provided.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be specifically described using the drawings.

In addition, in all the figures for explaining the embodiment, parts having the same functions are given the same reference numerals, and repeated explanations thereof will be omitted.

[Example I]

FIG. 1 is a perspective view for explaining the schematic configuration when the electrode of Example I, in which the present invention is applied to a distributed feedback semiconductor laser, is divided into three parts. This is a diagram with the .

The difference between this embodiment I and the conventional embodiment (Fig. 4) is that p
The bottom of the electrode separation groove lO of the side electrode 9 is located in the current block Wj7 made of 11-type IIIP or the current block layer 6 made of p-type 1nP. Here, the distance between the active layer 1 and the electrode separation groove 10 is indicated by d.

Hereinafter, two embodiments will be explained along FIG. The bottom of separation 1g1o is n type 1
so that it is located in the current blocking layer 7 made of nP or ρ) or the current blocking layer 6 made of IN-type InP. ] The side electrodes 9 are divided by electrode separation grooves 1 ( ). Then, a voltage is applied to the P-side electrode 9 of tI2 divided by the electrode division Kikuzo 10, and 2. Current is injected into the active layer 1 to obtain optical outputs 11 and 11', and when the device is in operation, the pn junction between the current blocking layers 6 and 7 becomes reverse biased, and current injection into the region is blocked. It has become so.

Here, if the electrode saving length of each of the divided p-side electrodes 9 is 100 μIT1, then (the resistance between the nine divided p-side electrodes 9 and the n@electrode 8 is about 5Ω, 1. However, if the electrode separation by the electrode separation grooves iO&llX is inadequate, the resistance between adjacent electrodes can easily become 1.
It becomes less than OOΩ.

However, according to the first embodiment, the electrode separation groove 10 is dug down to the current blocking layer 7 or 6 so that the distance between the electrode separation groove 10 and the active layer is dL. Therefore, the separation resistance between the electrodes has a thickness of d, which is approximately equal to the width of the light emitting region, and after the width of the electrode separation groove 10, it becomes approximately equal to the resistance of the material of this cladding layer 3 (0.3Ω・cm),
With a groove width of several μ[n], a resistance of 00Ω or more can be easily obtained. If the trench width is about several μm, the length of the region of the active layer (2) where no current is injected tb becomes almost negligible. In this way, the separation resistance can be increased by digging the electrode separation groove 10 down to the current blocking layer.

The characteristics of the force element were measured by applying the present invention, and a separation resistance of 500Ω was obtained with an electrode separation groove width of 5 μn1. The current-optical output characteristics of these devices were comparable to those of devices without electrodes, and devices having wavelength sweep widths of 1 nm or more were easily obtained.

As can be seen from the following explanation, according to the present embodiment (2), the p-side electrode 9 can be electrically sufficiently connected without deteriorating the characteristics of the distributed feedback type semiconductor laser (semiconductor light emitting device) and without losing L2. The active layer 1 can be separated by the separation groove 1o, and the oscillation wavelength of the device can be changed by flowing current non-uniformly through the active layer 1.

In addition, since the P-side electrode 9 is electrically separated by four electrodes, a modulation signal can be applied to one of the separated P-side electrodes 9, and it is affected by the heat generated by the modulation signal. Stable modulation characteristics can be obtained without any problems.

Further, the bottom of the electrode separation groove io that separates the p-side electrode 9 is n
Current plotter made of InP type N7 or p type 1 n
By simply processing the current block M6 to be located in the current block M6 made of P, it is possible to provide a distributed feedback type semiconductor 1 nozer (semiconductor light emitting device) having the above-mentioned characteristics with a high yield.

[Example ■]

FIG. 2 is a perspective view for explaining the schematic configuration when the electrode of Example 2 is divided into three parts in which the present invention is applied to a distributed feedback semiconductor laser. This is a diagram with .

Here, while in Example I, the current flow was stopped β11 by reverse biasing the pn junctions of the current blocking layers 7 and 6, in Example 2, the same effect was achieved by using the high resistance layer 12. This is what I did to get it. That is, 1) the current blocking layer composed of type and n-type semiconductors for confining the current to the light emitting region is a high resistance layer.

The effectiveness of this Example IN is clear.

Further, in this embodiment IN, the effect is 1 minute even when there is no cladding layer 3 between the high resistance layer 1υ and the cap layer 4.

[Embodiment IIN] FIG. 3 shows the present invention in a distributed feedback type single conductor laser t, -
It is a perspective view for explaining the schematic structure when the electrode of the applied example (2) is divided into three parts, with a part removed so that the inside of the device (n) can be described.

Here, while in the above-described embodiment I, the flow of fl is blocked by reverse biasing the pn junction between the current blocking layers 7 and 6, in the above-mentioned embodiment 2.

On the other hand, in the present embodiment (2), a high resistance layer 12 is included in the current block M6 of the above-mentioned embodiment I, and the same effect as that of the above-mentioned embodiments (2) and (2) is obtained. This is intended to achieve a similar effect. In other words, the effectiveness of Example 2 in which a high resistance layer is included in the current blocking layer made of p-type and n-type semiconductors for confining the current to the light emitting region is as follows.

This is clear from Examples I and (2) above. Also, high resistance M
The effect is the same no matter where 12 is placed.

The above embodiments I to (2) have been explained as examples in which the present invention is applied to an InGaAsP/InP-based distributed feedback semiconductor laser, but the present invention is also effective in devices made of other materials such as AlGaAs or Fabry-Perot semiconductor lasers. Needless to say. Further, in the description of the above embodiment, the current blocking layer is made of two layers, but a current blocking layer consisting of two or more layers is also effective. Moreover, the same effect can be obtained even if the conductivity type of each layer in the example is reversed.

The present invention has been specifically explained above based on examples, but
It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit thereof.

〔Effect of the invention〕

As described above, according to the present invention, the electrodes can be sufficiently electrically separated without deteriorating the characteristics of the semiconductor light emitting device, and by non-uniformly flowing current through the active layer, the device oscillates. The wavelength can be changed.

Furthermore, since the electrodes are electrically separated, a modulation signal can be applied to one of the separated electrodes without being affected by heat generation due to the modulation signal.

Stable modulation properties can be obtained.

Further, by simply forming the separation groove so that the bottom of the electrode separation groove reaches the current blocking layer, a semiconductor light emitting device having the above characteristics can be provided with a high yield.

[Brief explanation of the drawing]

FIG. 1 is a perspective view illustrating a schematic configuration of an electrode divided into three parts in Example I in which the present invention is applied to a distributed feedback type semiconductor laser. Figure 3 is a perspective view for explaining the schematic configuration when the electrode of Example 2, in which the present invention is applied to a semiconductor laser, is divided into three parts. FIG. 3 is a perspective view for explaining the schematic configuration when divided into two parts. FIG. 4 is a perspective view for explaining the problems of the conventional InGaASPI/InP distributed feedback semiconductor laser. In the figure, 1- InGaAsP active layer, 2- InGaA
sP guide layer, 3-p type InP cladding layer, 4-p type I
nGaAsP cap layer, 5... n-type InP substrate, 6
...P-type InP current blocking layer, 7...n-type InP
Current blocking layer, 8...n-side electrode, 9...p-side electrode, IO...electrode separation groove, 11.11'...light output,
12...High resistance layer, d...Distance m between the bottom of the electrode separation groove and the active layer.

Claims (1)

[Claims] (1) At least one of the positive and negative electrodes is an electrode separated into two or more by a physical separation groove, an active layer where light emission occurs, and a p-type electrode for confining current to the light emitting region. and a semiconductor light emitting device comprising a current blocking layer made of an n-type semiconductor, wherein the bottom of the electrode separation groove reaches the current blocking layer.