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Proceedings Paper

High-power and high-temperature FET technology
Author(s): Jehn-Huar Howard Chern; R. Jennifer Hwu; Laurence P. Sadwick
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Paper Abstract

The performance of heterojunction metal-semiconductor-field- effect-transistors (MESFETs) and junction-field-effect- transistors (JFETs) fabricated with different buffers is presented. For the JFET, carbon was chosen as the p-type dopant because of its relative low diffusivity compared to other doping elements. The viability of heterojunction MESFET and JFET devices operating at 400 degrees C have been demonstrated. Two key factors contributing to the reduction of drain leakage currents were the use of a high resistivity, undoped AlAs buffer layers and the gate contacting layers: n-type AlGaAs for the MESFET and p-type AlGaAs for the JFET. A two LT-AL0.3Ga0.7As layer scheme were used for the first time specifically for use in high temperature applications. Even at 400 degrees, C the gate leakage current density for a gate length of 2 micrometers was 9 by 10-7 A/micrometers at Vds equals 3V Vgs equals -7. The high resistance of LT-AlGaAs materials after annealing was responsible for such low gate leakage currents. The p- HEMTs became leaky at high temperature because of the parallel conduction and buffer design. The gate diode performed better when contacted to the undoped AlGaAs layer. DC and high-temperature performance of GaN-based MESFETs and MODFETs were compared. Al0.3Ga0.7N/GaN MODFETs with a gate-length of 2micrometers exhibited high transconductance was 47mS/mm, and dropped by 12 percent of its initial value to 41.4 mS/mm at 350 degrees C. The decrease in transconductance with temperature can be explained by the temperature dependence of the electron mobility. The large conduction band discontinuity in this material system may play an important role in terms of better electron confinement thus resulting in less degradation in transconductance.

Paper Details

Date Published: 18 December 2000
PDF: 15 pages
Proc. SPIE 4111, Terahertz and Gigahertz Electronics and Photonics II, (18 December 2000); doi: 10.1117/12.422151
Show Author Affiliations
Jehn-Huar Howard Chern, Univ. of Utah (United States)
R. Jennifer Hwu, Univ. of Utah (United States)
Laurence P. Sadwick, Univ. of Utah (United States)

Published in SPIE Proceedings Vol. 4111:
Terahertz and Gigahertz Electronics and Photonics II
R. Jennifer Hwu; Ke Wu, Editor(s)

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