CRYSTAL AND SUBSTRATE OF CONDUCTIVE GaAs, AND METHOD FOR FORMING THE SAME

Abstract

An electrically conductive GaAs crystal has an atomic concentration of Si more than 1×1017 cm−3, wherein density of precipitates having sizes of at least 30 nm contained in the crystal is at most 400 cm−2. In this case, it is preferable that the conductive GaAs crystal has a dislocation density of at most 2×10−2 cm2 or at least 1×10−3 cm2.

Description

TECHNICAL FIELD[0001]The present invention relates to a crystal and a substrate of electrically conductive GaAs, and more particularly to reduction in size and density of precipitates contained in the crystal and substrate of conductive GaAs.BACKGROUND ART[0002]Microscopic concavities and convexities on a surface of a semi-insulating GaAs substrate are liable to cause structural defects of an epitaxial layer or a semiconductor device formed on the substrate. Therefore, substrates having many microscopic concavities and convexities on their surface are determined as faulty during screening in an optical inspection and adversely affect the yield of products. In some cases the microscopic concavities and convexities detected during the optical inspection are caused by sticking of minute particles generated during wafer processing of the substrate, in others they are caused by the crystal itself.[0003]It is considered that arsenic precipitates anchored to dislocations are main cause for...

AI Technical Summary

Benefits of technology

[0015]According to the present invention, it is possible to obtain a crystal and a substrate of conductive GaAs in which sizes and density of precipitates contained therein are reduced.

Problems solved by technology

Microscopic concavities and convexities on a surface of a semi-insulating GaAs substrate are liable to cause structural defects of an epitaxial layer or a semiconductor device formed on the substrate.

Therefore, substrates having many microscopic concavities and convexities on their surface are determined as faulty during screening in an optical inspection and adversely affect the yield of products.

In the case of conductive GaAs substrates for laser devices in particular, however, in association with miniaturization of the devices and increase in the yield due to innovation of the production technique, the microscopic concavities and convexities on the substrate surface lead to structural defects of the semiconductor devices and are liable to often cause problems.

However, cause for microscopic concavities and convexities on the conductive GaAs substrate is not clear at all from the fact that the substrate cut from the conductive GaAs crystal usually includes less microscopic concavities and convexities on its polished surface as compared with the semi-insulating GaAs substrate and the fact that the density of microscopic concavities and convexities on the conductive substrate is hardly reduced even when the post-annealing is carried out similar to the case of the semi-insulating substrate.

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