Thermal and mechanical degradation mechanisms in heterostructural field-effect transistors based on gallium nitride

Vadim M. Minnebaev

Russian Technological Journal. 2025;13(2):57–73

Abstract

Objectives. Gallium nitride heterostructural field-effect transistors (GaN HFET) are among the most promising semiconductor devices for power and microwave electronics. Over the past 10–15 years, GaN HFETs have firmly established their position in radio-electronic equipment for transmitting, receiving, and processing information, as well as in power electronics products, due to their significant advantages in terms of energy and thermal parameters. At the same time, issues associated with ensuring their reliability are no less acute than for devices based on other semiconductor materials. The aim of the study is to review the thermal and mechanical mechanisms of degradation in GaN HFETs due to the physicochemical characteristics of the materials used, as well as their corresponding growth and post-growth processes. Methods for preventing or reducing these mechanisms during development, production, and operation are evaluated.
Methods. The main research method consists in an analytical review of the results of publications by a wide range of specialists in the field of semiconductor physics, production technology of heteroepitaxial structures and active devices based on them, as well as the modeling and design of modules and equipment in terms of their reliable operation.
Results. As well as describing the problems of GaN HFET quality degradation caused by thermal overheating, mechanical degradation, problems with hot electrons and phonons in gallium nitride, the article provides an overview of research into these phenomena and methods for reducing their impact on transistor technical parameters and quality indicators.
Conclusions. The results of the study show that strong electric fields and high specific thermal loading of high-power GaN HFETs can cause physical, polarization, piezoelectric and thermal phenomena that lead to redistribution of mechanical stresses in the active region, degradation of electrical characteristics, and a decrease in the reliability of the transistor as a whole. It is shown that the presence of a field-plate and a passivating SiN layer leads to a decrease in the values of mechanical stress in the gate area by 1.3–1.5 times. The effects of thermal degradation in class AB amplifiers are more pronounced than the effects of strong fields in class E amplifiers; moreover, the mean time to failure sharply decreases at GaN HFET active zone temperatures over 320–350°C.
Keywords: GaN HFET,  heterostructure, dual-channel HFET, coupled-channel HFET, current, self-heating, thermal conductivity, degradation, doping