Invalidity dossier
US 5393990
HEMT structure
Current assignee: Infineon Technologies North America Corp
Added 9/21/2026, 3:36:02 AM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 5393990 A ("HEMT structure")
Bibliographic data (from the supplied text): Title: "HEMT structure." Inventor: Erhard Kohn. Original assignee: Siemens Corporate Research Inc.; current assignee listed as Infineon Technologies North America Corp. Application No. US 07/980,870, filed 1992-11-24 as a continuation of Ser. No. 07/333,207 filed 1989-04-04 (now abandoned); priority date 1989-04-04; granted/published 1995-02-28. Status: Expired – Fee Related; anticipated expiration 2012-02-28. Classification includes H10D30/4755 (modulation-doped HEMTs such as n-AlGaAs/GaAs HEMTs).
Purpose: The patent relates to field effect transistors, particularly high electron mobility transistors using gallium arsenide technology. A HEMT is a heterostructure of GaAs and AlGaAs; the heterojunction confines conduction electrons in an undoped GaAs buffer layer as a two-dimensional electron gas (2DEG), supplied from donor ions in an AlGaAs donor layer. The text states that DX-centers lie within the conduction band for AlGaAs only when the aluminum mole fraction is below about 0.2 or above about 0.7, so practice had used mole fractions of 0.2 or less — limiting the conduction-band difference, potential-well capacity, mutual conductance, current capacity, and high-frequency performance.
Plain-language scope: A HEMT with source, drain, and control (gate) electrodes comprises a GaAs buffer layer and an AlGaAs donor layer. The donor layer's composition profile has relatively high aluminum over a first thickness portion near the buffer, low and generally constant aluminum over a second portion distal from it, and a graded aluminum concentration in a third, intermediate portion. Its doping profile has a relatively high doping spike in the first thickness portion and relatively low doping over the second and third portions. A dependent aspect places the high-aluminum region and doping spike in a thin portion and drops aluminum step-wise to a negligibly small value toward the gate interface, with the doping spike substantially contained in the thin portion.
Not established by the excerpt: the full claim set and claim language, all drawing details, the complete specification, exact cited prior art, and omitted text. Source: https://patents.google.com/patent/US5393990/en
Generated 10/1/2026, 10:02:39 PM
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