JPS63177485A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To reduce the capacitance of a device and to improve the high-frequency response characteristic of a laser by a method wherein high-resistance semiconductor layers are formed on the right side and on the left side of an active layer and an electrode pad to bond an electrode wire is formed only above the high-resistance semiconductor layer. CONSTITUTION:High-resistance semiconductor layers 9 are formed on the right side and on the left side of an active layer 3 for a semiconductor of buried structure; an electrode pad 13 to bond an electrode wire is formed only on the high-resistance semiconductor layers. For example, an n-InP buffer layer 2, an undoped In0.59-Ga0.41As0.90P0.10 active layer 3, a p-InP clad layer 4 and a p-In0.72Ga0.28As0.61P0.39 contact layer 5 are grown on an n-InP substrate 1. After that, a mesa stripe 6 including the active layer 3 is formed; mesas 7, 8 are formed on both sides of the stripe. Then, after an SiNx film has been formed on the mesa stripe 6 and the mesas 7, 8 and has been grown selectively, Fe-doped InP high-resistance layers 9 are grown. After that, an SiO2 insulating film 10, a P-type electrode 11 and an n-type electrode 12 are formed; an electrode pad 13 is formed only above the upper face of the high-resistance layer 9.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to semiconductor lasers.

[Conventional technology]

Buried structure semiconductor lasers (BH-LD) are capable of low threshold current, high output, and high temperature operation, and have therefore entered the stage of practical use as light sources for optical fiber communications. BH-
LD usually has p-n-p-n on the left and right sides of the buried active layer.
The structure is formed to form a current blocking layer to efficiently confine the injected current to the active layer. However, this structure does not sufficiently improve high-frequency characteristics, and it has recently been revealed that a structure in which high-resistance semiconductor layers are formed on the left and right sides of the active layer to reduce the capacitance of the device is effective. For example, Tanaka et al.
d Ph-ysica Letters magazine (Vol.
47, p. 1127), we developed the H-LD. This BH-LD has a structure in which two parallel grooves of mesa stripes including the active layer are sandwiched, and high-speed operation characteristics are obtained by burying a high-resistance semiconductor layer in these grooves. The resistivity of the high resistance semiconductor layer is 10
The capacitance of 'Ω·cm is IOPF, and the bias value is twice the dark value, and the 3 dB modulation band at time t is approximately 4 GHz.

[Problem that the invention seeks to solve]

By the way, when trying to further increase the speed of the H-LD as mentioned above, the electrode structure also needs to be devised.Basically, the area of the electrode can be reduced, but if the area of the conventional structure is Even if it is reduced, the capacitance component of the epitaxial layer in the electrode portion still remains, and there is a limit to the reduction in capacitance.

[Means for solving problems]

The present invention provides a semiconductor laser with a buried structure in which an active layer is covered with a semiconductor layer having a larger energy gap and a lower refractive index than the ambient sound. In this structure, electrode pads for bonding are provided only on the high-resistance semiconductor layer.

Further, the structure is such that the high-resistance semiconductor layer on which the electrode pad is provided is provided on a semi-insulating semiconductor substrate.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 (al) and FIG. 1(b) show the first embodiment of the present invention, and FIG. 1 (al is a plan view and FIG. BH-LDf of this example: To obtain the BH-LDf of this example, first, a non-doped In0. 59 Ga
O,41As0.90P0.10 active layer (thickness 0.1μ
m) 3, p-InP '17 rad layer (thickness 2a
m)+.

and p-I n O, 72 with an emission wavelength of 1.3 μm.
Ga O, 28 A's O, 6i Po, 39 contact layer (thickness 0.5 μm) 5 f is grown. Thereafter, all etching is performed to form a mesa stripe 6 including the active layer 3 for light emission recombination and mesas 7.8 on both sides of the mesa stripe 6. The mesa stripe 6 had a height of 3 μm1 and a width of 1.5 μm in the active layer 3 portion. Also, mesa 7.8 has a width of 1
It was set to 0 μm. A SiNx film is formed on mesa stripe 6 and mesa 7.8, and all selective growth is performed as it is. Fe-doped nP high resistance layer (high resistance semiconductor layer) 9 is grown with gold. TMIn.

By adopting PH3, Fe (C5H5) 2 t-↓9, obtain a high resistance layer with a resistivity of about 10Ω・cm. The growth temperature was 650°C. After that, 5in2 insulating film 10.
A partially provided P-type electrode 11 and an entirely provided N-type electrode 12 were formed, and the desired BH-LDi was obtained by cutting into individual laser chips. The electrode pad 13 for wire bonding has a size of about 50×50 μm2, and is formed only on the upper surface of the high resistance layer 9. As a result, the high frequency characteristics of the device are significantly improved, with a thousand passance of 6PF, and a K-tone band of 3dB and 7GHz compared to conventional devices.The basic characteristics as a t0 laser are a threshold current of 2QmA and a differential quantum efficiency of 50.
%, maximum CW output cuff 0mW, maximum CW operating temperature 120
A device of about 'O' was obtained with good reproducibility.

Next, referring to FIGS. 2(al) and 2(bl t-) showing a plan view and a sectional view taken along line A-B of a second embodiment of the present invention, semi-insulating In is used as a substrate in this embodiment.
A P substrate 15 is used, and on this substrate 15, buffer %, z, active layer 3°, cladding layer 4. After successively growing the contact layer 5 and the contact layer 5, etching is performed to the depth of the semi-insulating InP substrate 152 only on the 10,000 sides of the mesa stripe 6, and the InP high resistance layer 9 is similarly grown. Here, the entire circumference of the substrate 15 has a resistivity of 10 6 Ω·cm or more. Thereafter, the left side of the mesa stripe 6 in FIG. BH-L
D″f: obtained. In this case, the electrode pads 12 and 13 are all 50×50 μm2 in size, and in particular, the P-type electrode 11
Since the electrode pad 13 is formed only on the high resistance layer 9 and there is no conductive epitaxial layer between it and the substrate 15, it is possible to further reduce the capacitance of the device. When high frequency characteristics were evaluated, the capacitance was 4.
．． An even greater improvement was observed with a 5PF and 3dB modulation band of 9GHz.

In each of the above embodiments, ■nP, InGaA, and P-based semiconductor materials such as gold were used;
.

Similar implementation is possible using a semiconductor material such as GaA3.

It can also be applied to te%DFB laser, DBR laser, etc.

〔Effect of the invention〕

As explained above, according to the present invention, the capacitance of the device can be significantly reduced by providing the wire bonding electrode pad only on the high-resistance semiconductor layer. As a result, the high frequency response characteristics of the laser can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 (al and FIG. 1(b) are block diagrams showing a first embodiment of the present invention, and FIG. 2 (al and FIG. 2 (bl) are block diagrams showing a second embodiment of the invention. 1...substrate, 2...buffer layer, 3...
...Active layer, 4...Clad layer, 5...
...Contact layer, 6...Mesa stripe, 7, 8...Meb, 9...High resistance semiconductor layer, 13...Others Pad, 15...
Cow insulation engineered nP board. evil 1 figure

Claims (2)

[Claims] (1) In a semiconductor laser with a buried structure in which an active layer is surrounded by a semiconductor layer with a larger energy gap and a smaller refractive index, high-resistance semiconductor layers are provided on the left and right sides of the active layer, and electrode wires are bonded. 1. A semiconductor laser characterized in that an electrode pad is provided only on the high-resistance semiconductor layer. (2) The semiconductor laser according to claim 1, wherein the high-resistance semiconductor layer on which the electrode pad is provided is provided on a semi-insulating semiconductor substrate.