JP2536713B2 - AlGaInP semiconductor laser device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a light source for information processing equipment such as bar code readers and optical discs.
The present invention relates to an lGaInP semiconductor laser, and particularly to a laminated structure of the semiconductor.

[0002]

2. Description of the Related Art At present, in AlGaInP semiconductor lasers, improvement of high temperature operation characteristics is strongly desired. Two methods have been taken to improve it. One of them is a method of introducing a multilayer thin film structure adjacent to the active layer to reflect electron waves and suppress the overflow current from the active layer even at high temperature operation (Japanese Patent Laid-Open No. 63-46788). Another one
One is to increase the p-carrier concentration in the p-cladding layer and raise the Fermi level to effectively increase the barrier height between the active layer and the cladding layer (Journal of Quantum Electronics Volume 27 pages 1476-148).
2).

[0003]

The latter method of increasing the p carrier concentration in the p-clad layer described in the section of the prior art is a very simple method. However, actually, when a large amount of Zn which is a p-type impurity in the p-clad layer is introduced to increase the carrier concentration, the introduced Zn diffuses into the active layer 1 as conceptually shown in FIG. It forms a light emitting center, shortens the carrier life, and raises the threshold current. Conversely, from the viewpoint of suppressing Zn diffusion, Zn
It is necessary to suppress the doping amount to a certain degree, and it is not possible to increase the concentration above a certain concentration (up to 5 × 10 ¹⁷ cm ⁻³ ). Further, in the former method (method of providing the multilayer thin film structure adjacent to the active layer) described in the section of the conventional technique, it is necessary to select the layer thickness and the composition of each layer in an extremely strict relationship,
Atomic level control is required for manufacturing, and there are many problems in practical use. Therefore, an object of the present invention is to provide the former method described in the prior art with a new function and solve the latter problem.

[0004]

The AlGaInP of the present invention
The semiconductor element has A in a clad layer having p-type conductivity.
A multi-layer thin film structure in which AlGaInP layers having different l compositions are alternately laminated is arranged adjacent to the active layer, and tensile strain is applied to at least a layer having a small Al composition among the AlGaInP layers forming the multi-layer thin film structure. It is characterized by The configuration will be described with reference to FIG. The active layer 1 has a DH structure sandwiched by AlGaInP cladding layers 3 and 4. The active layer 1 may be either a so-called MQW formed of a multi-layer semiconductor thin film or a single-layer bulk semiconductor layer. A multilayer thin film structure 2 is arranged adjacent to the active layer 1 in the p-AlGaInP cladding layer 4. The multi-layered thin film structure 2 includes (Al _x Ga _1-x ) _z In _1-z P layer and (A
It becomes in a _{l y Ga 1-y) q} In 1-q P layer is formed by laminating layers having different Al composition alternately. y ≧ x, which is a layer having a small Al composition (Al _x Ga _1-x ) _z I
In order to apply tensile strain to the n _{1 -z} P layer, (Al _x G
_{a 1-x) z In 1} -z Al in the P layer _x Ga _1-x composition z is are selected. The substrate for crystal growth of the DH structure is G
If aAs, when z> 0.5 (Al _x Ga _1-x ).
_A tensile strain is applied to the _z In _{1 -z} P layer. On the other hand, q is 0.
It may be larger or smaller than 5.

[0005]

It is known that the diffusion constant of Zn in GaInP decreases as the amount of Ga solid phase increases. For example, 850
The diffusion constant of Ga _0.48 In _0.52 P at ℃ is 1.3 × 10 ^-9
cm ² / sec and Ga _0.6 with an increased amount of solid phase Ga
In _0.4 P is 0.8 × 10 ⁻⁹ cm ² / sec, and the diffusion constant is small. In addition, multi-layered AlGa with internal strain
The interface of the InP layer tends to trap Zn. This 2
Due to two effects, the structure of the present invention in which the multilayer thin film structure 2 is introduced into the P-AlGaInP cladding layer 4 has a function of suppressing diffusion of Zn into the active layer 1. Therefore P-AlG
The Zn atom concentration in the aInP cladding layer 4 can be further increased, which increases the acceptor concentration and suppresses carrier overflow. Here, the difference between the present invention and the conventional superlattice structure (multi-electron barrier) (JP-A-63-46788) will be clarified again from the viewpoint of the effect. Although the conventional superlattice structure is a structure similar to the multiple thin film structure of the present invention, the thickness of each layer and the vacuum level must be determined so as to reflect incident electron waves. Therefore, in the conventional superlattice structure, the relationship of composition with respect to layer thickness must be selected strictly. The structure of the present invention has no limitation on the layer thickness and is an invention that can be further added to the conventional superlattice structure. Conversely speaking, the multilayer thin film structure in the present invention is provided to function as a Zn diffusion suppressing layer, does not require consideration of the phase condition with the electron wave, and when the phase condition is deviated. Also effective in.

[0006]

EXAMPLES The present invention will be further described with reference to the following examples of the present invention.
This will be specifically described. Destruction of the structure in which the present invention is specifically implemented
A schematic view of the surface is shown in FIG. This structure is a metalorganic decomposition vapor phase
Crystals were laminated by the long method (MOVPE method). Well
First, an n-type GaAs buffer is formed on the n-type GaAs substrate 9.
-Layer 8 is laminated by 0.5 μm and then 0.9 μm thick of n-type A
lGaInP clad layer 3, undoped GaInP / A
From the active layer 1 and the active layer 1 having the lGaInPMQW structure
10 nm thick (Al_0.7 Ga_0.3 )_0.5 In _0.5 P layer 4
Multilayer thin consisting of GaInP / AlGaInP via a
Membrane structure 2, 0.9 μm thick p-type (Al_0.7 Ga_0.3 )
_0.5 In_0.5 P clad layer 4, Ga having a thickness of 0.3 μm
_0.5 In_0.5 The buffer layer 6 made of P is sequentially stacked.
Was. The active layer 1 is made of Ga having a thickness of 6 nm._0.6 In_0.4 P
With a thickness of 4 nm (Al_0.5 In_0.5 )_0.5 In_0.5 P
Is an MQW with four wells having a barrier. Multi-layer thin
The film structure 2 has a thickness of 10 Å Ga_0.6 In_0.4 P and thickness 2
0Å (Al_0.7 Ga_0.3 )_0.5 In_0.5 Alternating with P
It is a laminate of 10 layers. 10 nm thick (Al_0.7G
a_0.3 )_0.5 In_0.5 The P layer 4a is n-type or
Whether it is p-type or and-soap
Without support, p-type impurities from the p-type clad layer 4 during use
Diffuse and become p-type. A stripe pattern is formed on this wafer.
Turned SiO₂ GaInP as a film mask
The buffer layer 6 and the P-AlGaInP cladding layer 4 are
Partially etched to form mesa structure, then n
Type current blocking layer 5 made of GaAs on both sides of the mesa
Layered. Further SiO₂ After removing the film, the entire surface is GaA
The structure of FIG. 3 was prepared by covering with the s-cap layer 7. p side and
An electrode is formed on each of the n-side surfaces, and cleaving
The element was cut out to complete the element.

[0007]

In order to clarify the effect, an element having the multilayer thin film structure 2 and an element having no multilayer thin film structure 2 were formed while changing the doping amount in the p-clad layer. When the carrier concentration of the p-clad layer was 1 × 10 ¹⁷ cm ⁻³ , both oscillation thresholds were high and there was no difference between them. Carrier concentration is 4 × 10 ¹⁷
At cm ³ , both oscillation thresholds decrease and no difference is observed. The characteristic temperature of the oscillation threshold is 30 to 40 k, and no significant difference is observed here. Further, a large difference appeared in the element in which the carrier concentration was increased to 8 × 10 ¹⁷ cm ^-3 . In the device without the multi-layered thin film structure 2, the threshold value lowered at 4 × 10 ¹⁷ cm ^-3 again increased greatly. On the other hand, in the element in which the multilayer thin film structure 2 is introduced, the threshold value is 4 × 10.
^There is no change compared to the case of ¹⁷ cm ^-3 , and its characteristic temperature is 60
rose to k. This is due to the effect of the present invention that the multilayer thin film structure 2 suppresses the Zn diffusion shown in FIG. 2 and the p-cladding layer carrier concentration is maintained high.

[Brief description of drawings]

FIG. 1 is a schematic view showing a structure of an active layer and a clad layer sandwiching the active layer in a semiconductor laser device of the present invention.

FIG. 2 is a conceptual diagram showing how Zn in a clad layer 4 diffuses into an active layer 1.

FIG. 3 AlGaInP implemented by introducing the structure of the present invention
Schematic sectional view of a semiconductor laser.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Active layer 2 Multilayer thin film structure 3 n-AlGaInP clad layer 4 p-AlGaInP clad layer 5 Current block layer 6 GaInP buffer layer 7 GaAs cap layer 8 GaAs buffer layer 9 GaSa substrate 10 Low Al composition AlGaI which comprises a multilayer thin film structure
nP layer 11 High Al composition AlGaI constituting a multilayer thin film structure
nP layer

Claims (2)

(57) [Claims] 1. Different Al compositions (Al _x Ga _1-x )
_Z In _1-z P layer and the _{(Al y Ga 1-y)} q In 1-q P layer (y ≧ x) and a multilayer thin film structure are alternately laminated, one of the cladding layers sandwiching the active layer from both sides Of the two AlGaInP layers that have the p-type conductivity type and are adjacent to the active layer in the AlGaInP clad layer and that have the multi-layer thin film structure, the Al composition is the smallest (Al _x Ga _1-x ) _z In _{1- When the} tensile strain is applied to the zP layer, the above (Al _x Ga _1-x ) _z In
An AlGaInP semiconductor laser device, wherein a composition ratio z of Al _x Ga _1-x in the _1-z P layer is selected. 2. A semiconductor laminated structure in which the active layer is sandwiched by cladding layers is formed on a GaAs substrate by crystal growth, and the composition ratio z is 0.5 or more. The AlGaInP semiconductor laser device described.