Compound semiconductor epitaxial wafer

Details Compound semiconductor epitaxial wafer Compound semiconductor epitaxial wafer

1998-10-21

2000-05-02

Hardy, David B.

Active solid-state devices (e.g., transistors, solid-state diode

With specified impurity concentration gradient

Stepped profile

257655, 257190, 257191, H01L 29167

Patent

active

060575921

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a compound semiconductor epitaxial wafer and method for fabricating the wafer and more particularly, to a compound semiconductor epitaxial wafer containing gallium arsenide phosphide GaAs.sub.z P.sub.1-z (where 0.ltoreq.z.ltoreq.1) having a predetermined alloy composition.


BACKGROUND ART

In red-, orange- and yellow-color light emitting diodes, there has been conventionally employed an epitaxial wafer in which an epitaxial layer of gallium arsenide phosphide GaAs.sub.z P.sub.1-z (where 0.ltoreq.z.ltoreq.1) is formed on a single-crystalline substrate of gallium phosphide GaP or gallium arsenide GaAs.
When a lattice mismatching between the single crystal of the substrate of gallium phosphide GaP or gallium arsenide GaAs and the GaAs.sub.z P.sub.1-z epitaxial layer having an alloy composition formed on the substrate is large, this causes a misfit dislocation to take place at its interface, whereby a stress caused by the lattice mismatching is relaxed. When this dislocation propagates a composition constant layer, however, this results in that the internal quantum efficiency of the light emitting diode drops.
In order to relax such a lattice mismatching, there has been conventionally employed such an arrangement that an alloy composition gradient layer having a gradually varied alloy composition is provided as an interface between a single-crystalline substrate and a composition constant layer. That is, within the alloy composition gradient layer, an alloy composition gradually ascends along a thickness direction of the layer from an alloy composition of the single-crystalline substrate to a predetermined alloy composition of the composition constant layer. However, this results in that a stress caused by the lattice mismatching gradually accumulates in the entire epitaxial layer and amounts to a larger stress. This leads to generation of a misfit dislocation in the composition constant layer, with the result of reduction in lifetime and reduction in luminance.
For this reason, it has been so far demanded to develop a novel epitaxial wafer which can solve two problems that a misfit dislocation is propagated to the composition constant layer and that a stress caused by the lattice mismatching is exerted on the entire epitaxial layer.
This invention has been made for the purpose of solving the aforementioned problems or defects in the prior art, and an object of this invention is to provide a compound semiconductor epitaxial wafer which is high in luminance, quality and productivity.


DISCLOSURE OF INVENTION

For the purpose of solving the above problems, the inventors of the present application have studied hard how to prevent a misfit dislocation from propagating to a composition constant layer and to effectively eliminate a stress caused by lattice mismatching; and have found from their studies that it is good not to lower the ascending rate of an alloy composition to provide a moderate composition change as known as common knowledge in the prior art, but, to the contrary to the prior art, to provide an abrupt change of the alloy composition and immediately thereafter to somewhat descend the alloy composition backward moderately.
That is, the inventors have noted that the alloy composition is abruptly ascended at appropriate positions in a layer thickness direction in order to locally relax a stress accumulated distributedly in the layer thickness direction due to the lattice mismatching, and immediately thereafter the alloy composition is partially descended moderately thereby to prevent reduction of a crystal quality, and that part of the layer whose alloy composition was abruptly ascended is used as a reflective layer to return light upwardly passed therethrough in the substrate direction to thereby improve a luminance.
Therefore, the inventors, on the basis of such a novel knowledge as mentioned above, have developed a compound semiconductor epitaxial wafer which will be explained below.
That is, in order to realize the above object, there is provided a compou

REFERENCES:
patent: 4582952 (1986-04-01), McNeely et al.
patent: 4865655 (1989-09-01), Fujita et al.
patent: 5751026 (1998-05-01), Sato et al.

Affiliated with

Also associated with

Rating

Compound semiconductor epitaxial wafer does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Compound semiconductor epitaxial wafer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compound semiconductor epitaxial wafer will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1595912