JPS60154587A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To obtain an AlGaAs laser having long life by forming a P type second clad layer, the size of forbbiden band width thereof lies between an active layer and a P type first clad layer and which uses Ge as an impurity, between both layers. CONSTITUTION:An N type AlyGa1-yAs clad layer 2, a P type or N type AlxGa1-xAs active layer 3, a P type AlzGa1-zAs second clad layer 4, a P type AlvGa1-vAs first clad layer 5 and an N type GaAs cap layer 6 are grown on an N type GaAs substrate 1 in succession, and a current constriction constitution is formed by a striped selective diffusion region 7 consisting of Zn. The Al mixed crystal ratios of each AlGaAs layer have the relationship of y, v>z>x. Ge is used as an impurity in the layer 4 and Mg or Zn as an impurity in the layer 5. The diffusion coefficient of Ge is remarkably smaller than that of Mg or Zn, and Ge does not diffuse even during a high-temperature process on crystal growth. Accordingly, the movement of a P-N junction and the deterioration of the crystallizability of the active layer can be prevented, and long life can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Description of the technical field to which the invention pertains] The present invention relates to a long-life KlG (JtB) laser.

[Description of prior art]

The conventionally used N! I; Many of the aA6 lasers are p
4 or 4 is used as the type cladding layer impurity. This is JG5A (which has a large M mixed crystal ratio compared to G#).
This is because there is an advantage that the carrier density can be increased even in the s-cladding layer, and the electrical resistance of the element can be reduced. However, these impurities easily diffuse into surrounding layers such as the active layer and bean-type cladding layer during the high-temperature process during crystal growth, causing deterioration of device characteristics and life. A part of the outer cladding layer may be converted into a p-type layer due to the diffused metal oxide, and a p-n junction may be formed at a position away from the active layer. In such an element,
The threshold current value is high and the efficiency is low due to poor carrier injection efficiency into the active layer.If this is prevented by increasing the carrier density in the S-type cladding layer, a large amount of impurities doped into the N-type cladding layer will cause the problem. As a result, terraces are formed on the surface of the n-type cladding layer, causing new problems such as uneven thickness of the active layer formed thereon and loss of crystallinity.

Furthermore, in any case, it is inevitable that vacancies and interstitial atoms are formed in the active layer due to the movement of p-impurity atoms, and these crystal defects cause device deterioration. Therefore, its lifespan was short.

[Detailed description of the invention]

Purpose of the present invention Improves the above-mentioned conventional drawbacks and provides a long-life A7.
! The purpose of the present invention is to provide a GaAs laser.

[Detailed description of the invention]

The present invention uses an impurity KG between the AlzGal-zAs active layer (0<z<1>) and the first p-type Mρa1-υAs cladding layer, with a forbidden band width between the two layers. This is an M-al-as laser characterized by providing a pmMG (IA8 second cladding layer (,<g<v)).

[Explanation of Examples]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic diagram of a first embodiment of the invention.

In FIG. 1, there are L-types G and A, and an n-type camphor on the substrate 1.

cladding layer 2, p-type or n-type 1'JJat-included 8
Active layer 3, 'I) mAAtzc (Ll-gAB second cladding layer 4, p-type Mραl-τA8 first cladding layer 5,
After sequentially growing the n%G cap layer 6, a current confinement structure is formed by stripe-like selective diffusion (region 7), and a p-side electrode 8 is provided on the front surface and an n-side electrode 9 is provided on the back surface to form a planar structure. This is a striped laser.

Each A7! The M mixed crystal ratio of the GaAs layer has a relationship of y, v>z>π.

G is used as an impurity in the cladding layer 4 of the p-type cylinder 2, and G or 4 is used as an impurity in the p-type first cladding layer 5. G# has a property that it has a significantly smaller diffusion coefficient than G#4, and does not diffuse even during the high temperature process of 750 to 800° C. during crystal growth. The second layer in contact with this active layer 3
By using G as the p-type impurity of the cladding layer 4,
Movement of the PN junction and deterioration of the crystallinity of the active layer can be prevented, and a long life can be achieved. On the other hand, the carrier density that can be achieved by doping (G) into the JGaAs layer is smaller than that achieved by using a scoop or a cup, and the value decreases as the M mixed crystal ratio increases. If the M mixed crystal ratio 2 of the cladding layer 4 is kept low, the layer thickness is made thin, and the carrier density is made sufficiently high by using impurities of 1/nt or 7/nt for the first cladding layer 5, the electrical resistance of the element can be reduced. The value can be made small enough for practical use.

For example, in the case of a braided laser with an oscillation wavelength of 0.78 μm, which is most widely used as a light source for optical information processing, the M mixed crystal ratio (Q<z<1), layer thickness, and electrical resistance are as follows. become. The active layer 30M mixed crystal ratio 2 is 0.15. It is said that in order to provide a sufficient heterobarrier to trap injected carriers in the active layer, it is necessary to make the M mixed crystal ratio of the cladding layer 0.3 or more higher than that of the active layer. The cladding layer 50M mixed crystal ratio is set to 0.45. At this time, impurity Kh! If you use ig, 4 XIO”am-”
A carrier density of approximately 2×10”Ω can be achieved, and a specific resistance of approximately 2×10”
Tiny and small. On the other hand, the carrier of the p-type cylinder 2 cladding layer 4
When the M mixed crystal ratio 2 is 0.45, the density is limited to 1×1017 or less, whereas when 2 is set to 0.35, 2 to 3×101″cIL−” can be achieved.

The specific resistance at this time is approximately 0.2Ω·me. The thickness of the first cladding layer is as thick as 1.5 degrees, and the thickness of the second cladding layer 5 is as thick as 0.5 degrees.
Make it as thin as 5 μm. The electrical resistance of the element is determined by the resistance of the p-type AiG layer (A8), which has low carrier mobility, so from the layer thickness and specific resistance mentioned above, the resonator length is 300 mm, and the width of the current band stripe 7 is 12 μm. If we estimate the electrical resistance of a conventional laser element, we can obtain a value as small as approximately 0.49, which is sufficiently small for practical use.As with conventional elements, the plumes in the first cladding layer 5 are formed during the high-temperature process during crystal growth. However, the distance is 0.2~0.34!.Thickness is 0.
．． Since the second cladding layer 4 with a thickness of 5 μm separates the active layer 3 and the first cladding layer 5, martyred atoms do not reach the active layer 4.
, the crystallinity of the active layer 4 is not impaired. On the other hand, since the conductivity type of the n-type cladding layer is not reversed due to peak diffusion, the carrier density can be set to a single value, for example, 5 XIO" am-3, which does not cause problems such as formation of terraces. It is assumed that the M mixed crystal ratio V is 0.45.At this time, the specific resistance is as small as lXl0''-''Ω·儂, and its contribution to the element resistance can be ignored.

FIG. 2 is a schematic diagram of a plano-convex waveguide mmG laser according to a second embodiment of the present invention. In this embodiment, stripes ^1-v with a plano-convex cross section are formed between the active layer 3 and the n-type cladding layer 2.
This is an M laser that enables stable fundamental transverse mode oscillation by providing the As waveguide layer 10 (g<y). In order to form a plano-convex waveguide layer IO, an n-type G, zA8 substrate 11 on which an IC groove has been formed in advance is used, and an n-type cladding layer 2 is formed thereon, leaving a depression in the groove. The other points are made in the same manner as in the first embodiment. Identical components are given the same numbers and their explanations will be omitted. G for impurities
Due to the effect of the second cladding layer using ε, it is possible to realize a long-life M-~ laser in which the transverse mode is controlled without impairing device characteristics such as electrical resistance.

FIG. 3 is a schematic diagram of an embedded type MG laser according to a third embodiment of the present invention. In this example, the I'JGaA-a multilayer thin films 2 to 7 epitaxially grown on the i8 substrate 1 were selectively etched to a depth reaching the n-type GaA substrate in the same manner as in the first example. After, p m, A
Al18Gct-aA first buried layer 211s type AJtG
, l-4Aa second buried layer 22 is grown to bury the mesa part, and 4 is further diffused into the mesa part to form an insulating Sin film 2.
3. Create by forming p-side and n-side electrodes 8 and 9 on the front and back sides. According to this embodiment, the buried type M! has a low threshold current value, maintains the device characteristics of high efficiency, and has a long life due to the effect of the second cladding layer 4 using the impurity KG! GaA
, a laser can be realized.

[Detailed description of the invention]

As described above, according to the present invention, K maintains the electric resistance of the device at a sufficiently small value for practical use, and prevents the movement of the PN junction and the crystal deterioration of the active layer, which occur in conventional devices, resulting in a long life. ) This has the effect of making it possible to obtain a JGaAs laser device.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the laminated structure of a planar strip type 8 laser according to the first embodiment of the present invention, and FIG. 2 is a diagram showing the laminated structure of a plano-convex waveguide type AllGaAs laser according to the second embodiment of the present invention. FIG. 3 is a diagram showing a stacked structure of a buried type A□aAs laser according to a third embodiment of the present invention. 1...n-type G, A, substrate, 2...n-type 1'-1f;
ax-ykg cladding layer, 3...p type or n type M
Slut αl-Hair 8 active layer, 4...p fjl IJ Slut αl
- 8 second cladding layer, 5... p-type AJ. GCLz-1Ag first cladding layer, 6-n-type GaA3
Cap layer, 7... p-type impurity diffusion region, lO...
n-type A4cQ. , - plano-convex optical waveguide layer, 11...grooved n-type G-8 substrate, 21...p-type A11sGa*-a
As 1st jM embedded layer, 22.=s type AltGax-t
l Second buried layer, 23...SjO, thin film Figure 1 Figure 2

Claims (1)

[Claims] (1) AJ + ρa1 - IA sclerotic columnar layer 0 < Z < 1) and the first
'I) K between fJiMvGGI-嘗A8 cladding layer
, an AJG-8 semiconductor laser characterized by providing a p-type M^l-^ second cladding layer (g<g<w) using an impurity KG and having a forbidden band width intermediate between both layers. Element, −