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Producing a new form of GaAs

IP.com Disclosure Number: IPCOM000084924D
Original Publication Date: 1976-Jan-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Welber, B: AUTHOR

Abstract

A new type of semiconductor has been prepared by hydrostatically compressing a sample of crystalline GaAs which normally has a band gap of 1.4 eV. As the pressure is increased, the band gap increases steadily to about 2.7 eV at a pressure of 180 KBar.

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Producing a new form of GaAs

A new type of semiconductor has been prepared by hydrostatically compressing a sample of crystalline GaAs which normally has a band gap of 1.4 eV. As the pressure is increased, the band gap increases steadily to about 2.7 eV at a pressure of 180 KBar.

Attempts to increase the pressure further result in an abrupt phase transformation which is optically observed. This transformation is irreversible, so that when the material is brought back to normal atmospheric pressure a new high-density form of GaAs is retained, which is stable. This new material has a band gap which is only 0.7 eV.

The crystal structure of this new phase when the pressure is reduced back to atmosphere is different than for the starting material. The crystal structure of the new phase is of much lower symmetry than the Zn-blende type structure which is the normal GaAs structure. This new structure has been indexed as simple tetragonal D/8/(4) type, having lattice parameters a = 6.1 angstroms and c = 7.5 angstroms. The new phase is stable at normal temperatures and pressures.

The band gap of GaAs increases linearly with pressure and becomes increasingly transparent in the range of visible wavelengths. Initially, it was transparent only to infrared radiation, but at higher pressures it transmits wavelengths from 5000 angstroms up to the infrared range. Therefore, the application of pressure can be used to tune GaAs lasers and light-emitting diodes.

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