JPS6289386A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To reduce the leakage current to such extent that it becomes negligible by forming the laminar structure on a semiconductor substrate, which is composed of a semi-insulating first semiconductor layer, a second semiconductor layer of the first conductive type whose forbidden band gap is narrower than that of the first semiconductor layer, a third semiconductor layer of the first conductive type whose forbidden band gap is wider than that of the second semiconductor layer and forming P-N junctions in the second and third semiconductor layers. CONSTITUTION:On a GaAs substrate 13, an undoped AlxGa1-xAs layer 17, undoped GaAs layer 3 which is to be an active layer, and Se doped N-type AlxGa1-xAs layer 4 are grown in order by epitaxy using an organic metal gas-phase growth technique. On the grown layers, an SiO2 or SiN film is deposited and a predetermined region is removed by etching into stripe form to expose the surface of the grown layer. Zn is diffused to form a Zn diffusion region 5. After the above SiO2 or SiN film is removed by etching into stripe form of 10mum, a P-type electrode and an N-type electrode are arranged on the Zn diffusion region 5 and the non-diffused electrode, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a semiconductor laser device that is used in the field of information processing and has a low bibase current and excellent temperature characteristics.

2. Description of the Related Art A conventional semiconductor laser device of this type is as shown in FIG. 2, for example. Figure 2 shows a TIS laser, and the characteristics of this TJS laser are, for example,
E E Journal of Quantum
Electronics)QE-11p-427(19
75), but there is one serious drawback. The laser shown here has a low threshold current and oscillates in a single mode, but there is a large leakage current that does not contribute to oscillation, and as the temperature rises, this leakage current increases rapidly and eventually stops oscillating due to heat generation. Stop and do it. This TJS laser has a second
As shown in the figure, an n-type GaAs substrate 1 is used,
A j2 G a As layer 2. GaAs layer 3°71,
After forming the ItGaAs layer 4 and laminating a double heterostructure of the same conductivity type as the substrate, a second conductivity type determining impurity is diffused from a predetermined region of the surface layer to form a diffusion region 5 to form a pn A junction is formed, and the three-vane diffusion front reaches the substrate, forming a pn junction within the substrate as well. When a voltage is applied between the electrodes 10 and 110 in the forward direction,
Current flows to the pn junction in the active layer 3 and the pn junction in the substrate. The current flowing into the pn junction within the substrate not only does not contribute to light emission at all, but is also the main cause of heat generation, shortening the lifespan.

In order to eliminate this leakage current to the substrate, there is a semiconductor laser device with a structure as shown in FIG.
0-11478). This structure is similar to the conventional n-type G
a Semi-insulating Ga containing Cr in place of the A s substrate
An As substrate 13 is used, and the Zn diffusion region 5 containing Zn reaches the substrate 13.

Since the substrate 13 is made of Cr-doped GaAs, the electrode 10 provided in contact with the Zn diffusion region 5
On the other hand, the electrode 12 is provided in contact with the n-AnGaAs layer 4. Although the Zn diffusion front has reached the substrate 13, a resistivity of about 1069m can be easily obtained as a Cr doped substrate 13, which is about 1% lower than the resistivity of the grown layer.
0 times, and no current flows through the substrate 13.

Problems to be Solved by the Invention However, with this structure, leakage current that does not contribute at all to laser oscillation is Aj! It flows into the GaAs layers 2 and 4. Although the magnitude of leakage current is reduced compared to the conventional structure shown in FIG. 2, there is still a problem that affects the oscillation characteristics. The present invention provides an innovative semiconductor laser device that further reduces this leakage current and significantly improves the oscillation characteristics of the laser.

Means for Solving the Problems The technical means of the present invention for solving the above problems is to provide at least a semi-insulating first semiconductor layer on a semiconductor substrate;
A stacked structure is formed of a second semiconductor having a first conductivity type whose forbidden band width is narrower than that of the first semiconductor layer, and a third semiconductor layer having a first conductivity type whose forbidden band width is wider than that of the second semiconductor layer. a second conductivity type determining impurity is added from a predetermined region on the surface of the third semiconductor layer, and first and second electrodes are provided in contact with the regions having the first and second conductivity types. It is.

6 vanes For production The effect of this technical means is as follows.

That is, the undoped AJ2GaAs layer grown by metal organic chemical vapor deposition (MO, CVD) has a resistivity of 1o6.
Since it shows a high resistance of Ω(7) or more, AJ2Ga in Figure 3
If the As layer 2 is changed to an undoped AjlL GaAs layer, the leakage current that does not contribute to laser oscillation at all is the current flowing through the AlGaAs layer 4, and the leakage current can be significantly reduced. Since the leakage current flows only through the top layer AρGaAs layer 4, by attaching a heat sink, the heat generated by the leakage current can be significantly suppressed, and the characteristics of the laser are significantly improved.

Embodiments Below, embodiments of the present invention will be described based on the accompanying drawings. In FIG. 1 showing an embodiment of the present invention, a Gr-doped GaAs substrate 13 is formed by H2BO3:H2O2:H
20=5:1:1 (7) :r-near f
After notching, MOCVDMetal Organic
Chemical Vapot Deposition
) set in the map position. A non-doped 6-vanop A f! on the GaAs substrate 13. , x Ga 1-x As layer 17 (x:
o, 3, 11tm).

Undoped GaAs layer 3 (0,2μ
m) and Se-doped n-type A 1 x Ga 1
-x As layer 4 (x: 0.3° 1 μm) is formed by sequential epitaxial growth.

Undoped An x Gal formed by MOCVD method
The -x As layer (X≧0.1) exhibits good high resistance with a resistivity of approximately 10 Ωm or more, and the undoped GaAs layer exhibits high quality n-type with a carrier concentration of 10 or less.

An 8102 or SiN film (not shown) is deposited on the grown layer by CVD or sputtering, and predetermined areas are etched away in stripes to expose the surface of the grown layer.
Zn diffusion region 5 is formed by diffusing Zn at 680° C. for 40 minutes. The diffusion depth is approximately 3 μm. After removing the St○2 or SiN film in stripes of 10 μm, a p-type electrode such as Au is formed on the Zn diffusion region 5.
/Zn10° In the non-diffused region, an n-type electrode such as Au/5
n12 are provided respectively.

GaAs has a narrower forbidden band width than AρGaAs, so the diffusion potential of the GaAsp%n junction is lower than that of AlGaAs.
As is lower than that of the p7 pane n junction, when a voltage is applied between the electrodes 10.12, the current mostly flows through the GaAs pn junction 15;
Laser oscillation occurs in this part. However, AρGaA
Although the diffusion potential of the spn junction is high, there is also a small amount of current flowing across this barrier. This is a leakage current that does not contribute to laser oscillation at all. Conventional T
Simply changing the substrate to semi-insulating with the JS laser will cause the pn junction of the AlGaAs layer in contact with the substrate and the GaAs layer to be in contact with the substrate.
sThe other AlGa A for sandwiching the active layer
A leakage current that is not sufficient for laser oscillation flows through the pn junction of the s layer, but by making the AflGaAs layer 17 in contact with the substrate an undoped semi-insulating layer, the leakage current is halved.

Conventionally, heat generation caused deterioration of characteristics, but with the present invention, deterioration of characteristics due to leakage current is no longer a problem.

In the examples of the present invention, a Gr-doped GaAs substrate was used, but an undoped GaAs substrate or a Si
A doped n-type GaAs substrate may also be used.

Effects of the Invention As described above, the semiconductor laser device of the present invention includes a semi-insulating first semiconductor layer on a semiconductor substrate, a first conductivity type whose forbidden band width is narrower than that of the first semiconductor layer. A laminated structure is formed by a second semiconductor layer and a third semiconductor layer having a first conductivity type whose forbidden band width is wider than that of the second semiconductor layer.
A second conductivity type determining impurity is added from a predetermined region on the semiconductor layer of the second. A pn junction is formed in each third layer, and first and second electrodes are provided in contact with regions having the first and second conductivity types, thereby directing current to the second semiconductor layer. By concentrating it on the pn junction, the leakage current can be reduced to a negligible level, the threshold current can be reduced, and the temperature change in the threshold current can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a semiconductor laser device according to an embodiment of the present invention, FIG. 2 is a perspective view of a conventional semiconductor laser device, and FIG. 3 is a sectional view of a conventional semiconductor laser device. 3--undoped GaAs layer, 4--n AI
V, GaAg layer, 9 Vane 5--=Zn diffusion region, 17...-undoped A fl
GaAs layer, 13--Cr-doped Ga
As substrate, 10.12...electrode.

Claims (2)

[Claims] (1) On a semiconductor substrate, at least a semi-insulating first semiconductor layer, a second semiconductor layer having a first conductivity type whose forbidden band width is narrower than that of the first semiconductor layer, and a second semiconductor layer whose forbidden band width is narrower than the first semiconductor layer; A laminated structure is formed with a third semiconductor layer having a first conductivity type wider than that of the second semiconductor layer, a second conductivity type determining impurity is doped from a predetermined region on the third semiconductor layer, and a second conductivity type determining impurity is added to the second semiconductor layer. ,
A semiconductor laser device comprising first and second electrodes that form a pn junction in each third layer and are in contact with regions having the first and second conductivity types. (2) The semiconductor laser device according to claim 1, wherein the first semiconductor layer is formed of undoped high-resistance AlGaAs.