Electrical characterization, modeling and reliability of electronic devices grown on wide band gap semiconductors (SiC and GaN)
The general objective of this research topic is the characterization and evaluation of the degradation effects induced by high Electric Fields and hot carriers in AlGaN/GaN devices, for high power applications. The research activity includes both the analysis of the open/closed channel breakdown phenomena in DC and Pulse regime, and the study of the degradation effects caused by thermal stress and hot carriers damages. The different degradation mechanisms have been carefully studied through several available. The main two research activities are: 1. Electrical characterization of GaN HEMT devices for microwave and millimeter-wave power applications, with particularly attention to the parasitic effects and breakdown. 2. Evaluation of the reliability of GaN HEMT under electrical and thermal stresses. Particularly, the devices are stressed through both high drain voltage values, in order to study the hot electron degradation effects, and thermal cycles, in order to better individualize the degradation mechanisms caused by the temperature heating.
Main results: The most important and original results have been:
1) Traps formation and their effects on the GaN HEMT electrical characteristics have been characterized;
2) Energetic carriers (hot electrons) effects on the devices electrical characteristics have been completely identified and understood;
3) GaN-HEMTs device behavior in breakdown regime has been studied.
4) The GaN HEMT devices reliability problems have been analyzed in detail through an extensive number of lifetime accelerated tests under different test conditions (high temperature, high currents, high electric fields,….)
5) Breakdown mechanisms have been identified in devices under lifetime accelerated tests through electrical and analytical techniques (Emission Microscopy, SEM,..).