The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 03, 1990
Filed:
May. 02, 1988
Masao Yamane, Kokubunji, JP;
Tomoyoshi Mishima, Shiki, JP;
Shigeo Goto, Kokubunji, JP;
Susumu Takahashi, Tokyo, JP;
Makoto Morioka, Tokyo, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A compound semiconductor structure in the form of a superlattice film with effectively graded average composition, comprising an alternating lamination of two kinds of layers of different composition to form pairs of layers, the ratio of the thickness of one layer to the thickness of the other in said pairs of layers being gradually varied in the direction of thickness throughout successive pairs, thereby the average composition being effectively graded throughout the pairs. In a hetero-junction field effect transistor, the layer of effectively graded composition is used between a semiconductor layer making low resistance contact with a current-supplying electrode and a semiconductor layer where a two dimensional channel is to be formed. In case of AlGaAs/GaAs system, the Al composition is varied. When the superlattice film is heat-treated, Al in the AlGaAs layer diffuses into the GaAs layer, yielding a film with actually smoothly graded Al mole fraction.