Accession Number:

ADA495738

Title:

The Effects of Temperature and Electron Radiation on the Electrical Properties of AlGaN/GaN Heterostructure Field Effect Transistors

Descriptive Note:

Master's thesis

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT

Personal Author(s):

Report Date:

2009-03-01

Pagination or Media Count:

120.0

Abstract:

AlGaNGaN Heterostructure Field Effect Transistors HFETs have come under increased study, in recent years, owing to their highly desirable material and electrical properties, ruggedness, and survivability even during and after exposure to extreme temperature and radiation environments. These devices or similar devices constructed of AlGaN andor GaN materials are being researched for their potential applications in many military and space based systems. In this study, unpassivated and SiN passivated Al0.27Ga0.73NGaN HFETs were subjected to electron radiation at incident energies of 0.5MeV and 1.0MeV and fluences from 5x10exp 14 to 5x10exp15 e-sq cm while maintained in a 10exp -6 Torr or higher vacuum at liquid nitrogen temperature LN. The primary focus of the research was the effects of electron radiation and temperature on drain current, gate leakage current, threshold voltage shift, and gate-channel capacitance. Measurements were taken of transistor current, gate-channel capacitance, and gate leakage current vs. gate bias at 4 deg K temperature intervals beginning at LN through room temperature RT. The resulting gate leakage currents were fitted to a Trap-Assisted Tunneling model and transistor currents were compared to a Charge Control model to evaluate post-irradiation change mechanisms to the parameters of these models. Post-irradiation drain currents increased for all devices, with a consistently lesser increase observed for passivated devices. Most post-irradiation increases returned to nearly pre-irradiation levels after an RT anneal period. Threshold voltage shifts averaged -0.5V for unpassivated and -0.2V for passivated HFETs, showed negligible temperature dependence, and returned to near pre-irradiation values, after RT anneal periods. Gate leakage currents showed post-irradiation increases for all devices.

Subject Categories:

  • Inorganic Chemistry
  • Electrical and Electronic Equipment
  • Electricity and Magnetism

Distribution Statement:

APPROVED FOR PUBLIC RELEASE