Accession Number : ADA141058

Title :   High Speed FETs Fabricated in GaAs/AlGaAs Layered Structures Prepared by Molecular Beam Epitaxy.

Descriptive Note : Annual progress rept. 31 Dec 82-31 Dec 83,


Personal Author(s) : Morkoc,H

PDF Url : ADA141058

Report Date : Jan 1984

Pagination or Media Count : 111

Abstract : The research on modulation doped AlGaAs/GaAs FETs (MODFETs) and on AlGaAs buffer GaAs MESFETs has continued with; substantial progress. Current-voltage collapse observed in the drain characteristics of MODFETs in dark at 77K have for the first time been eliminated. The responsible mechanisms were found to relate to the defect concentration in AiGaAs and also to the gate recess width relative to the gate. Microwave S-parameter measurements were also made to deduce the device equivalent circuit parameters and compared to conventional GaAs MESFETs. The results are compared qualitatively to predictions. In GaAs FETs with high resistivity AlGaAs buffer layers it was found that no improvement (relative to GaAs buffer FETs) but degradation can result if the AiGaAs buffer GaAs active layer interface is not of high quality. The only way high quality can be assured has been found to be via the use of a thin superlattice at the heterointerface. Both optical and electrical properties of the GaAs layer grown on this superlattice is of sufficiently high quality to lead the expected improvements in the device performance. With the super lattice AlGaAs/GaAs MESFETs better rf performance has been obtained.

Descriptors :   *Field effect transistors, *Epitaxial growth, *Gallium arsenides, *Doping, *Molecular beams, Crystal lattices, Interfaces, Electrical resistance, Equivalent circuits, Electric current, Modulation, Structures, Scalers, Degradation, Voltage, Parameters, Optical properties, Drainage, Thinness, Collapse, Layers

Subject Categories : Electrical and Electronic Equipment
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE