JP2921053B2 - Semiconductor light emitting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor light emitting device used for a communication, arithmetic or measuring device.

[Conventional technology]

In recent years, remarkable progress has been made regarding the high power of InGaAsP semiconductor lasers. This is because an embedding technique with a small leakage current has been established over a wide current range, and recently, a high output operation exceeding 200 mW has been realized at room temperature and pulse driving. With the advancement of such technology, fault detection of optical fiber (OTDP: Optical Time
Application as a light source for Domain Reflectometer, intersatellite communication in outer space, erbium-doped fiber (ED
It is expected as a light source for excitation of F: Er Doped Fiber) amplifier.

As such a high-power semiconductor laser, for example, Y. Sakakibara et al., Journal of Lightwave Technology, LT-3, pp. 978-983 (J. Ligh
As reported in twave Technology, vol. LT-3, pp 978-983 (1985)), after forming a V-shaped groove in a semiconductor layer having a reverse junction current blocking layer grown on a p-type semiconductor substrate. ,
A so-called buried crescent (B) in which a crescent-shaped active layer is formed by a liquid phase epitaxy (LPE) method
C)) There are structural semiconductor lasers. The advantage of the semiconductor laser using the p-type substrate in terms of high output is that the withstand voltage of the reverse junction current block layer is higher than that of the n-type substrate, and the electrical resistance of the n-type semiconductor on the junction is smaller. It is thought to be.

[Problems to be solved by the invention]

However, in a BC semiconductor laser, it is difficult to control the formation and filling of grooves, and a distributed feedback (DFB:
buted Feedback) structure. Also, for example, DC-PBH (Double Channel-Pla
When a p-type substrate is used in a buried structure (BH: Buried Heterostructure) semiconductor laser such as a nar Buried Heterostructure structure, the leakage current is extremely large due to the low resistance of the n-type current block, and a good BH laser is manufactured. It was difficult to do.

[Means for solving the problem]

According to the present invention, an active layer is provided on a semiconductor substrate, and a first semiconductor layer is provided on the active layer, a second semiconductor layer having a different composition from the semiconductor substrate at least between the semiconductor substrate and the active layer, and a second semiconductor layer A third semiconductor layer is provided between the active layer and the active layer, and a groove removed to at least the second semiconductor layer is provided on both sides of the light emitting region. Is made lower than the light emitting region, and the trench is filled with the current blocking layer. Thereby, the contact area between the first semiconductor layer on the active layer and the current blocking layer of the same conductivity type as the first semiconductor layer can be minimized, and even when the semiconductor layer is embedded. A good BH laser with low leakage current has been obtained.

Example 1 FIG. 1 shows a sectional view of a semiconductor laser according to the present invention.
Further, an example of the manufacturing method will be described in detail below with reference to FIG. The LPE method was used as a crystal growth method.

On a p-InP substrate 10, a p-InP buffer layer (carrier concentration p = 1 × 10 ¹⁸ cm ⁻³ ) 20 and a p-InGaAsP layer (p = 3 × 10
¹⁷ cm ^-3 ; thickness about 0.2 μm) 30, p-InP layer 40 (p = 1 × 10
¹⁸ cm ^-3 ; thickness about 1 μm), undoped InGaAsP active layer 50
(1.3 μm composition; thickness 0.5 μm), n-InP cladding layer 60
^{(N = 1 × 10 18 cm} -3) the successively grown (Figure 2 (a)). Thereafter, the Br-based etching solution to form a groove U-shaped (FIG. 2 (b)). Groove width is about 5μm, depth is about 3μm
It is. Then, after forming the photoresist 5 by photolithography, the n-InP layer 60, InGaAsP50, and p-InP layer 40 outside the groove are sequentially removed by selective etching (FIG. 2 (c)). After removing the photoresist 5, the LP
The p-InP block layer 70 (n = 1 × 10 ¹⁸ c
m ^-3 ), p-InP blocking layer 80 (p = 1 × 10 ¹⁸ cm ^-3 ) n-
An InP buried layer 90 (n = 1 × 10 ¹⁸ cm ⁻³ ) and an n-InGaAsP contact layer 95 were grown. According to this structure, the carriers flowing into the n-block layer 70 are recombined with the carriers injected from the p-InP 20 in the InGaAsP layer 30 on both sides of the groove, so that the current blocking region including the semiconductor layers 20, 70, 80, and 90 is formed. In order to suppress turn-on of the DC-PBH structure, it has the same advantages as the conventional DC-PBH structure.

500 semiconductor laser wafers formed by the above method
Cleavage was performed with a cavity length of μm, and the front and rear end faces were coated with a reflectance of 10% and 90%, respectively. After evaluating the device characteristics, the oscillation threshold value at room temperature was 15 to 20 mA. From this, it is considered that the leakage current is 5 to 10 mA, which is almost the same as that of the structure of the BH structure using the conventional n-type substrate. Therefore, according to the present invention, even in the BH structure using the p-type substrate, the n-cladding layer
The leakage current flowing to 60 could be suppressed to about 1/3 or less as compared with the case where the semiconductor layers 40, 50, 60 outside the trench were buried without being removed. Characteristic temperature is 90K near room temperature, high humidity area (50 ~ 90
60 ° C.). The maximum light output at 25 ° C is C
180 mW was obtained in W operation and 230 mW in pulse operation (pulse width 4 μs, duty 0.01).

Embodiment 2 A second embodiment of the present invention will be described with reference to FIG.

The difference between this embodiment and the first embodiment is that both the growth before the formation of the groove and the burying growth are performed by using the vapor phase growth method.

on the p-InP substrate 10, p-InP buffer layer (carrier concentration ^{p = 1 × 10 18 cm -3} ) 20, p-InGaAsP layer 125, p-InP
Layer 40 (p = 1 × 10 ¹⁸ cm ⁻³ ) 128, undoped InGaAsP layer 13
0, p-InP layer 40 (p = 1 × 10 ¹⁸ cm ⁻³ ; thickness about 1 μm),
Multiple quantum well structure active layer 150 (InGaAs well; thickness 75 mm;
7 layers, 1.2 μm composition InGaAsP barrier; thickness 150Å), n-In
After sequentially growing the P cladding layer 60 (n = 1 × 10 ¹⁸ cm ⁻³ ) by the MODPE (metal organic chemical vapor deposition) method, for example, using an insulating film such as SiO ₂ as a mask, U
A U-shaped groove is formed. The width of the groove is about 5 μm and the depth is about 3
μm. Thereafter, after forming a photoresist by photolithography, the n-InP layer 60 outside the trench, the multiple quantum well structure active layer 150, and the p-InP
The layers 40 are sequentially removed. Removing the photoresist, by leaving the SiO ₂ was used in etching the grooves, MOVPE
N-InP block layer 70 (p = 1 × 10 ¹⁸ c
m ⁻³ ), p-InP block layer 80 (n = 1 × 10 ¹⁸ cm ⁻³ ), n
-InP buried layer 90 (n = 1 × 10 ¹⁸ cm ⁻³ ), n-InGaAsP
Growing the contact layer 95, embedding the area other than the light emitting area,
The semiconductor laser shown in FIG. 3 is obtained.

By using the vapor deposition method, a device having good controllability and uniformity can be obtained, and a quantum well structure can be adopted, which has a great effect on improvement of device characteristics.

〔The invention's effect〕

As described above, according to the present invention, the leakage current flowing through the current block semiconductor buried layer can be minimized, and high output and high efficiency operation of the semiconductor laser can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention, FIG. 2 is a process diagram showing an example of a manufacturing method of the first embodiment, and FIG. 3 shows a second embodiment of the present invention. It is sectional drawing. 5 ... photoresist, 10 ... p-InP substrate, 20 ... p
-InP buffer layer, 30 ... p-InGaAsP layer, 40 ... p-In
P layer, 50: undoped InGaAsP active layer, 60: n-InP
Cladding layer, 70: n-InP block layer, 80: p-InP
Block layer, 90 ... n-InP buried layer, 95 ... n-InG
aAsP contact layer, 130 ... undoped InGaAsP layer.

Claims (4)

(57) [Claims] 1. A semiconductor device comprising at least an active layer and a first
Semiconductor layers are sequentially laminated, grooves are formed on both sides to be light emitting regions, and the grooves are further filled with a semiconductor layer. In a semiconductor light emitting device, at least the semiconductor substrate and the active layer have a composition between the semiconductor substrate and the active layer. A third semiconductor layer between the second semiconductor layer and the active layer, and a third semiconductor layer between the active layer and the second semiconductor layer.
A semiconductor light emitting device, wherein the semiconductor layer is removed up to at least the second semiconductor layer in the trench. 2. A semiconductor substrate comprising InP and a second semiconductor layer comprising InGaAs.
The semiconductor light emitting device according to claim 1, wherein P is P. 3. The semiconductor light emitting device according to claim 1, wherein the conductivity type of the semiconductor substrate is p-type. 4. The active layer has a multiple quantum well structure.
14. The semiconductor light emitting device according to claim 1.