JP2730683B2 - Semiconductor light emitting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor light emitting device, and more particularly to a visible light semiconductor laser device.

(Prior Art) Light emitting devices used for converting electric energy into light energy include light emitting diodes and semiconductor laser devices. The basic principle of the light emission phenomenon in these light emitting elements is spontaneous emission and stimulated emission. Spontaneous emission is applied to light emitting diodes, and stimulated emission is applied to semiconductor laser devices. In particular, a visible light semiconductor laser device capable of generating coherent visible light by stimulated emission has attracted attention as a light source in the fields of optical information processing and optical measurement, and in the field of optical communication using plastic fibers.

Such a visible light semiconductor laser device is, for example, GaAs.
(Al _z Ga _1-z ) _x In _1-x P lattice-matched with GaAs crystal on the substrate
The mixed crystal (x0.5,0 ≦ z ≦ 1) was prepared by metalorganic vapor phase epitaxy (M
It is produced by growing using an OCVD method or a molecular beam epitaxy method (MBE method).

2 (a), 2 (b) and 2 (c) are cross-sectional views showing the steps of manufacturing a conventional typical refractive index guided visible light semiconductor laser device.

First, as shown in FIG. 2A, an n-GaAs buffer layer 202, n- (Al _0.7 Ga _0.3 ) _0.5 In
_0.5 first cladding layer 203, Ga _0.5 In _0.5 P active layer 204, p- (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P second cladding layer 205, p-Ga _0.5 In
_{A 0.5P} first contact layer 208 and a p-GaAs second contact layer 209 are sequentially grown. Next, after a resist pattern is formed on the p-GaAs second contact layer 209, as shown in FIG. 2B, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P
The second cladding layer 205 is etched in a stripe mesa shape. Then, to embed this stripe mesa, p−
A GaAs third contact layer 211 is grown, an n-side electrode (AuGe) 213 is formed on the back surface of the substrate 201, and a p-GaAs third contact layer 211 is formed.
By forming a p-side electrode (AuZn) 212 on the surface of the semiconductor laser, a visible light semiconductor laser device as shown in FIG. 2C is obtained (K. Itaya et al., Jpn. J. Appl. Phys. 27 (1988) L
2414).

In this type of visible light semiconductor laser device, p- (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P The stripe-shaped portion of the second cladding layer 205 is an optical waveguide. Since the second cladding layer and the p-GaAs third contact layer 211 form a heterojunction, a discontinuous portion exists in the band structure of the valence band. Since the valence band barrier due to band discontinuity has a carrier barrier effect, current confinement can be performed using the heterojunction surface between the second cladding layer and the third contact layer.

(Problems to be Solved by the Invention) As described above, in the conventional manufacturing method, p- (Al _0.7 G
a _0.3 ) _0.5 In _0.5 P An optical waveguide is formed by etching the second cladding layer 205. This etching is performed for a predetermined time by a chemical or physical method. The end point of the etching is determined by the time regulation, and the remaining p-
The thickness of the plane portion of the (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P second cladding layer 205 is not directly monitored. Therefore, it is difficult to control the thickness of the plane portion of the second cladding layer, particularly to form the second cladding layer with a constant thickness with good reproducibility. As a result, the refractive index of the second cladding layer is not constant, and it is difficult to control the transverse mode of the obtained semiconductor laser device with good reproducibility.

Further, since the second cladding layer is made of a mixed crystal containing Al, the surface state is easily deteriorated when exposed to air. In this manufacturing method, after the etching step, the p-GaAs third contact layer 211 is grown on the remaining p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P second cladding layer 205. The layer will grow on the degraded crystal surface. Therefore, in the conventional manufacturing method, the crystal state of the third contact layer of the obtained semiconductor laser device is deteriorated. This causes a rapid deterioration of the device, particularly when the semiconductor laser device is operated at a high output.

An object of the present invention is to solve the above-mentioned conventional problems. An object of the present invention is to provide a semiconductor light emitting device which can perform transverse mode control with good reproducibility and does not deteriorate early even when operated at high output. It is an object of the present invention to provide a device, particularly a visible light semiconductor laser device.

(Means for Solving the Problems) The semiconductor light emitting device of the present invention comprises an n-GaAs substrate on which n
_{- (Al z Ga 1-z} ) x In 1-x first cladding layer consisting of P mixed crystal (0 ≦ x ≦ 1,0 ≦ z ≦ 1), (Al y Ga 1-y) v In 1-v P mixed crystal (0
≦ y <z, v ≒ 0.5) active layer, p- (Al _z Ga _1-z ) _x I
The second cladding layer made of n _1-x P mixed crystal, Ga _w In _1-w P mixed crystal (0
≦ w ≦ 1) consisting of an etching stop layer, narrower than the etching stop layer, p- is formed in a stripe shape in the etching stop layer _{(Al z Ga 1-z)} x I
A third cladding layer made of n _1-x P mixed crystal, a stripe-shaped third cladding layer and a p-GaAs contact layer covering the etching stop layer are sequentially formed, and a second cladding layer and a p-GaAs contact layer are formed between the second cladding layer and the p-GaAs contact layer. The current is confined by the valence band barrier and the valence band barrier between the third cladding layer and the p-GaAs contact layer, and the thickness of the etching stop layer is smaller than the de Broglie wavelength of the carrier and its quantum The level is set to be higher than the energy of light generated in the active layer, thereby achieving the above object.

(Operation) In the semiconductor light emitting device of the present invention, the second clad layer, the etching stop layer, and the third clad layer are sequentially formed on the active layer.

Since this etching stop layer is made of GaInP mixed crystal,
The etching conditions are different from those of the cladding layer made of AlGaInP mixed crystal. Therefore, it is possible to select an etching condition such that only the cladding layer is etched and the etching stop layer is not etched. When the third cladding layer is etched under such etching conditions,
Although the etching proceeds in the unmasked portion of the third cladding layer, when the etching reaches the etching stop layer, the etching stops and the thickness of the etching stop layer does not change. As a result, the thickness of the second cladding layer left after the etching is kept constant.

Further, since the etching stop layer does not contain Al, the surface state does not deteriorate even when exposed to air.
Therefore, the third contact layer grown on this is
The crystal state becomes good.

In the present invention, since the etching stop layer is formed to have a thickness smaller than the de Broglie wavelength of the carrier (about 200 °), the band discontinuity of the valence band between the second clad layer and the third contact layer is formed. Does not affect the function of. Therefore, a valence band barrier still exists between the second cladding layer and the third contact layer formed via the etching stop layer, and the carrier has a sufficient carrier barrier effect. As a result, the current confinement function using the valence band barrier is maintained as in the conventional example. Since the etching stop layer having such a thickness forms a quantum level, the etching stop layer can have a band gap larger than the energy of light generated in the active layer. Thus, by providing the etching stop layer that does not absorb the light generated in the active layer, the optical waveguide function of the third cladding layer formed in a stripe shape is maintained as in the conventional example.

(Example) An example of the present invention will be described below.

1 (a) to 1 (e) are cross-sectional views showing a manufacturing process of an AlGaInP-based visible light semiconductor laser device which is one embodiment of a semiconductor light emitting device according to the present invention. This semiconductor laser device was manufactured as follows.

First, as shown in FIG. 1A, an n-GaAs buffer layer (0.5 μm thick) 102, n- (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P First cladding layer (1.5 μm thickness) 1
03, Ga _0.5 In _0.5 P active layer (thickness 0.1 μm) 104, p- (Al _0.7
Ga _0.3 ) _0.5 In _0.5 P Second cladding layer (0.2 μm thick) 105,
p-Ga _0.5 In _0.5 P etching stop layer (thickness 30 mm) 10
6, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P Third cladding layer (thickness
_{1.4μm) 107, p-Ga 0.5} In 0.5 P first contact layer (thickness
500 °) 108, and p-GaAs second contact layer (thickness 0.5
μm) 109 were sequentially grown by MBE. Then, p−G
On the aAs second contact layer 109, a stripe-shaped resist pattern 110 having a thickness of 0.1 μm and a width of 5 μm was formed.

Then, as shown in FIG. 1 (b), the p-GaAs second contact layer 109 was etched in a stripe shape using an ammonia-based or sulfuric acid-based GaAs selective etchant.
Next, as shown in FIG. 1 (c), the p-Ga _0.5 In _0.5 P first contact layer 108 was etched in a stripe shape using a hydrochloric acid-based or bromine-based etchant. The end point of this etching is determined by time regulation. Then, after removing the resist pattern 110, the stripe-shaped p-GaAs second contact layer 109 and p-G
Using a _0.5 In _0.5 P first contact layer 108 as a mask and a sulfuric acid or phosphoric acid AlGaInP selective etchant, as shown in FIG. 1D, p- (Al _0.7 Ga _0.3 ) _0.5 I
The n _0.5 P third cladding layer 107 was etched in a stripe shape. On the p-Ga _0.5 In _0.5 P etching stop layer 106 thus exposed, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5
The third P-cladding layer 107, p-Ga _0.5 In _0.5 P-GaAs third contact layer (thickness 3.5 mm) is embedded by MBE so as to embed the first P contact layer 108 and the second p-GaAs contact layer 109.
μm) 111 was grown. Finally, by forming an n-side electrode (AuGe) 113 on the back surface of the n-GaAs substrate 101 and a p-side electrode (AuZn) 112 on the surface of the p-GaAs third tact layer 111,
A visible light semiconductor laser device as shown in FIG. 1 (e) was obtained.

Using the AlGaInP-based visible light semiconductor laser device thus obtained, a continuous operation test was performed at room temperature.
As a result, it was confirmed that the oscillation threshold current was 40 mA and that stable single transverse mode oscillation was achieved at an optical output of 20 mW or more.

For comparison, p-Ga _0.5 In _0.5 P etching stop layer
AlGaInP is formed in the same manner as in the above embodiment except that 106 is formed to have a thickness not less than the de Broglie wavelength (about 200 °) of the carrier.
System visible light semiconductor laser device was fabricated and tested under the same conditions. As a result, this semiconductor laser device did not oscillate at room temperature. This is because the valence band barrier formed between the second cladding layer and the third contact layer is separated on each side because the etching stop layer has a thickness greater than the de Broglie wavelength of the carrier. It is considered that a sufficient carrier barrier effect cannot be obtained.

In this embodiment, the example using the Ga _0.5 In _0.5 P active layer is shown, but the energy of light generated in the active layer is
As long as the band gap is smaller than the band gap of the GaInP etching stop layer, an AlGaInP mixed crystal can be used for the active layer, and the active layer can have a quantum well structure or a superlattice structure. As the cladding layer, an AlGaInP mixed crystal or an AlInP mixed crystal having a different composition from that of the embodiment can be used, and the cladding layer may be formed in a multilayer structure such as a SCH structure. Further, when growing the third contact layer, a liquid phase epitaxy (LBE) method or an MOCVD method may be used.

(Effects of the Invention) According to the present invention, the second clad layer can be formed with a constant thickness with good reproducibility, and the third contact layer having a favorable crystal state can be formed thereon. The lateral mode control can be performed with good reproducibility, and a semiconductor light emitting device, particularly a visible light semiconductor laser device, which exhibits stable characteristics without early deterioration even when operated at high output can be obtained.

[Brief description of the drawings]

1 (a) to 1 (e) are cross-sectional views showing a manufacturing process of an AlGaInP-based visible light semiconductor laser device which is an embodiment of a semiconductor light emitting device according to the present invention, and FIGS. 2 (a), (b) and FIG. 2C is a cross-sectional view showing a manufacturing step of the conventional visible light semiconductor laser device. 101,201 ... n-GaAs substrate, 103,203 ... n- (Al _0.7 Ga
_0.3 ) _0.5 In _0.5 P First cladding layer, 104, 204 ... Ga _0.5 In
_0.5 P active layer, 105,205 ... p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5
P second cladding layer, 106: p-Ga _0.5 In _0.5 P etching stop layer, 107: p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P third
Cladding _{layer, 108,208 ...... p-Ga 0.5 In} 0.5 P first contact layer, 109,209 ...... p-GaAs second contact layer, 111 and 211 ...
... p-GaAs third contact layer.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-314883 (JP, A) JP-A-63-43387 (JP, A) JP-A-2-172287 (JP, A)

Claims (1)

(57) [Claims] To 1. A n-GaAs _{substrate, n- (Al z Ga 1-} z) x In
_First cladding layer composed of _1- xP mixed crystal (0 ≦ x ≦ 1,0 ≦ z ≦ 1), (Al _y Ga _1-y ) _v In _1-v P mixed crystal (0 ≦ y <z, v) ≒ 0.5)
Active _{layer, p- (Al z Ga 1-} z) x In 1-x second cladding layer composed of P mixed crystal, an etching stop consisting of Ga _w In _1-w P mixed crystal (0 ≦ w ≦ 1) consisting of layers, narrower than the etching stop layer, is the _{p- (Al z Ga 1-z} ) forming a stripe shape by the etching stop layer _x in _1-x third cladding layer made of P mixed crystal, this Forming a stripe-shaped third cladding layer and a p-GaAs contact layer covering the etching stop layer sequentially, a valence band barrier between the second cladding layer and the p-GaAs contact layer, and a third cladding layer and the p-GaAs contact; The current is confined by the valence band barrier between the layers. The thickness of the etching stop layer is smaller than the de Broglie wavelength of the carrier, and the quantum level is larger than the energy of light generated in the active layer. Semiconductor light emitting device set in the same way.