JPS61139082A - Semiconductor light-emitting device - Google Patents

Abstract

PURPOSE:To obtain high luminous efficiency by forming constitution having buried type hetero-junction structure in which current stopping layers compensat ed by adding manganese are shaped on both the right side and the left side of a partially formed active layer. CONSTITUTION:The title device has buried type hetero-junction structure in which current stopping layers compensated by adding Mn are shaped on both the right side and the left side of a partially formed active layer. When high- resistance InP layers 11 are grown as the current stopping layers and currents are constricted, the trouble of the turn-ON of a thyristor in conventional P-N-P-N structure is eliminated, and currents do not leak from the current stopping layers, thus acquiring a buried type laser having high efficiency. A P-type impurity, such as Cd, Zn, Be, Mn, etc. is added to compensate said layers in order to shape the high-resistance InP layers 11 because InP having high purity displays an N-type under the state of non-addition, but Mn among them has characteristics in which it is difficult to be oxidized, hardly diffuses in the solid phase, has low toxicity, has a large acceptor level (approximately 230meV) and has low vapor pressure in the vicinity of the temperature of the growth of a liquid layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor laser device having a low threshold current.

Recently, optical transmission has been in the spotlight, and semiconductor lasers and light emitting diodes are used as light sources.

These light sources generally have a heterojunction structure of m-v compound semiconductors, and semiconductor lasers have a wavelength of 0.7 to 0.
．． 9 pm band AlGaAs/GaAs (active layer/
substrate) and InGaAs P/in the wavelength band of 1-1.5um
InP is famous, especially InGaAs P in the long wavelength band.
/ In P is regarded as the favorite light source for optical transmission.

In such semiconductor lasers, a buried structure is known, in which the side surfaces of an active layer provided in a stripe shape on a substrate are covered with a cladding layer, which provides high output and high luminous efficiency with a low threshold current. However, there is a demand for these semiconductor lasers to have as high performance as possible.

[Prior Art] FIG. 5 shows a schematic cross-sectional view of an InGaAs P/In P semiconductor laser device as an example of such a buried semiconductor laser, and 1 indicates an n''-InP substrate.

2 is n-InP buffer layer, 3 is n-InGaAs
P active layer, 4 p-1nP cladding layer, 5 p-In
GaAs P layer, 6 is p-InP layer (current blocking layer), 7 is n-1nP layer (current blocking layer), 8 is 5i0
2 film (silicon dioxide film: insulating film), 9 is raw electrode, 10
is one electrode.

Laser emission is performed in an n-1nGaAsP active layer 3, and an n-InP layer 7 and a p-InP layer 7 are formed on both sides as current blocking layers.
An InP layer 6 is formed, and a pnpn junction is formed between the upper and lower electrodes via this current blocking layer. In this way, the n-InP layer 7 and the p-InP layer 6 form a reverse junction, and the injected current is concentrated in the active layer (current confinement), and the current does not flow in the current blocking layer. A low oscillation threshold current can be obtained as shown in FIG.

[Problems to be Solved by the Invention] However, when creating such a buried structure, the n-InP buffer layer 2. n-InGaAsP
Active layer 3. p-4nP cladding layer 4. 'Q In
After the GaAsP cap layer 5 is epitaxially grown in a liquid or gas phase, the central portion is left in a mesa shape and both sides are etched away, and a second epitaxial growth is performed to form a p-rnP layer 6 and an n-InP layer. A forming method is adopted in which 7 and 7 are laminated.

However, it is very difficult to align the junction surface between the n-1nP current blocking layer 7 and the p-InP current blocking layer 6 exactly with the position of the n-InGaAsP active layer 3, and therefore, the n-InP layer 7 The bonding surface between the p-InP layer 6 and the p-InP layer 6 moves, creating a leakage path as shown by the arrow in FIG.

On the other hand, in this embedded structure, if we consider the path passing through the current blocking layer from the raw electrode 9 to the one electrode 10, that part has a pnpn structure as described above, and this can be considered as a cyrisk. Therefore, the leakage current due to the leakage path shown by the arrow is injected into the gate portion of the thyrisk, and serves to turn on the thyrisk.

In this case, there is a major drawback in that current blocking becomes incomplete, resulting in a decrease in luminous efficiency as the injection current increases.

The present invention proposes a semiconductor light emitting device having a structure that eliminates these drawbacks.

[Means for solving the problem] The problem is that on both the left and right sides of the partially provided active layer,
This problem is solved by a semiconductor light emitting device having a buried heterojunction structure provided with a current blocking layer which is compensated by adding Mn (manganese).

For example, this problem can be solved by creating a semiconductor light-emitting device having a buried heterojunction structure with an InP current stop layer, which is compensated by adding Mn (manganese) to both the left and right sides of an active layer made of n-InGaAsP. be done.

[Function] That is, in the present invention, a high-resistance current blocking layer similar to an insulator is formed without forming a current blocking layer that utilizes the reverse characteristics of a pn junction as in the conventional case.

In compound semiconductors, forming a high-resistance layer is not easy compared to forming a single semiconductor (eg, silicon or germanium). However, for example, M
If n is added to compensate, the resistance becomes high, and such a current blocking layer can be provided.

In this case, there is no leakage path due to the current blocking layer, no leakage current is generated, and high luminous efficiency can be obtained.

[Example] Examples will be described in detail below with reference to two drawings.

FIG. 1 shows InGaAs P/In according to the present invention.
A cross-sectional view of the structure of a P semiconductor laser device is shown, in which reference numeral 11 denotes a high-resistance p--InP layer doped with Mn (manganese), and other symbols are the same as those in FIG. 5 with the same symbols.

In this way, by growing the high-resistance InP layer 11 as a current blocking layer and confining the current, the problem of turn-on of the thyristor in the conventional pnpn structure is eliminated, and leakage from the current blocking layer is eliminated (thereby, high efficiency burying is achieved). type laser is obtained.

In order to form the high-resistance InP layer 11, Cd (cadmium
, Zn (zinc), Be (beryllium), Mn
It is compensated by adding p-type impurities such as M
n has the characteristics of being difficult to oxidize (low diffusion in the solid phase, low toxicity, large acceptor level (approximately 230 meV), and low vapor pressure near the liquid layer growth temperature, and is the most It is a suitable additive.

FIG. 2 illustrates the addition characteristics of Mn to InP, where the horizontal axis represents the MnO liquid phase composition ratio and the vertical axis represents the hole concentration of InP. As shown in the figure, the electron concentration (
If the residual donor concentration (residual donor concentration) is kept low at around 10"/cd1, the liquid phase composition ratio of Mn in the melt for liquid layer growth will be approximately 10"/cd1.
High resistance p- with 5 atomic % and hole concentration of about 10/-
- An InP layer is grown in a liquid layer with good reproducibility. The mobility of holes is about 100C11! / V, Sec, so at this hole concentration, InP has a high resistivity of about 100Ω.
You get layers.

To create the above melt for liquid layer growth, 0.2 μg of Mn is added to 1 g of In. To do this, you can create a low-concentration master alloy and dilute it.

Next, FIGS. 3(a) to 3(C) show cross-sectional views in the order of the formation process. First, as shown in FIG. 3(a), Sn(
Sn-doped n-I was grown by liquid layer epitaxial growth on an n''-1nP substrate 1 with a tin-doped (100) plane.
nP buffer layer 2. Additive-free n −1nGaAs P active layer 3. Cd-doped p-InP cladding layer 4. A Zn-doped p -1nGaAs P cap layer 5 is sequentially grown. This is the first liquid layer epitaxial growth.

Next, as shown in (in the same figure), a 5 μm wide S is formed in the center.
After providing a stripe mask of the iO□ film 12, the growth layers on both sides are etched until they reach the InP substrate 1.
Form into a mesa shape. This mesa etching is performed for about 5 minutes using a methanol solution containing O2% bromine.

Next, as shown in the same figure (C), the 5i02 film 12
Leave the mask as is and apply the liquid layer growth melt described above (
A second liquid layer epitaxial growth is performed using Mn-doped InP) to selectively embed a current blocking layer consisting of a p--4nP layer 11. The melt composition is In:InP:Mn=1 g:5.3mg:0.
At 2 μg, the growth initiation temperature is about 600°C.

Next, after removing the 5i02 film 12 mask, the 5i02
A film 8 is deposited, a window is opened on its surface to form ten electrodes 9 made of Au/Pt/Ti, and one electrode 10 made of Au-Sn is formed on the back side, completing the process as shown in Fig. 1. do.

Next, FIG. 4 shows a schematic sectional view of another embodiment according to the present invention. The embedded semiconductor laser in Figure 1 is a BH
This type is called the PBH type (Planned Heterostructure type).
-er Buried Heterostructure
This structure is called e-type).

This structure is formed by mesa etching (see FIG. 3(b)) in the formation process, and then the 5i02 film mask 12 and p
-1nGaAsP cap layer 5 is removed, and a second liquid layer epitaxial growth is performed until the surface is flattened.
Embed a current blocking layer. Then Cd or ZnO
A p+ region 13 is formed on the surface near the electrode by thermal diffusion or ion implantation of Be, Mg, or the like. This structure has the characteristic that electrode formation is easy because the surface is flattened, but this structure also has a current blocking layer made of high-resistance p--InP, similar to the BH type shown in Figure 1. It is formed of layers and similarly eliminates leakage paths to obtain high luminous efficiency.

[Effects of the Invention] As is clear from the above description, according to the present invention, there is an advantage that the leak path from the current blocking layer is eliminated, high luminous efficiency is obtained, and the performance of the semiconductor laser is improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a semiconductor laser device according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of a semiconductor laser device according to an embodiment of the present invention.
Figures 3(a) to (C1 are cross-sectional views in the order of the formation steps of the semiconductor laser device shown in Figure 1; Figure 4 is a schematic cross-sectional view of another semiconductor laser device according to the present invention; FIG. 5 is a schematic cross-sectional view of a conventional semiconductor laser device. In the figure, 1 is an n''-InP substrate, 2 is an n-InP buffer layer, 3 is an n-InGaAs'P active layer, and 4 is a p-InP layer. cladding layer, 5 is p-1nGaAs P cap layer, 6 is p-I
nP current blocking layer, 7 is n-InP current blocking layer, 8 is 5i02 film, 9 is ten electrodes, 10 is one electrode, 11 is p--
An InP current blocking layer, 12 a 5i02 film stripe mask, and 13 a p+ region. Figure 1.ゝ10 Figure 2 M? Figure 3 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) Mn (
1. A semiconductor light-emitting device characterized by having a buried heterojunction structure provided with a current blocking layer which is compensated by adding manganese. (2) InP with compensation performed by adding Mn (manganese) to both the left and right sides of the active layer made of n-InGaAsP
2. The semiconductor light emitting device according to claim 1, having a buried heterojunction structure provided with a current blocking layer.