Neutron Radiation Effects Research Of A Novel GaN Power Switching Transistor

GaN power switches have shown great potential in commercial and military applications with their high temperature resistance, high breakdown voltage, high power capacity and high frequency. Normally-off technology is one of attractive topics in GaN power switch researching field. Nevertheless, few research concerning radiation effects on normally-off GaN HEMTs has appeared in published papers. Analysis based on physical mechanism of the transistor implied that displacement damage may be the primary factor lead to degradation of normally-off HEMT. Therefore, conducting research on the neutron irradiation effect of GaN power switching devices is of great significance for evaluating the reliability of GaN-based power devices used in intense radiation environment.In this thesis, neutron radiation displacement damage effects and degradation rules for a novel normally-off GaN power switch----gate injection transistors(GIT) was studied by means of combining simulations and experiments. At first, the density of defects produced by neutrons with different fluxes in the transistor was calculated with Gent 4. Secondly, a numerical structural model and basic characteristic of GIT were developed with Silvaco Atlas module, and potential displacement effects were analyzed by embedding traps in the model. Finally, the experiments to investigate the displacement effects of GITs were conducted in a reactor with 1 Me V fast neutron radiation environment, and the experiment results are to some extent in line with the simulation.It is concluded in this thesis that displacement damage mechanism and neutron radiation effects of GITs are different from conventional GaN HEMTs due to their sophisticated structures. When the neutron flux reaches 1.6×1014cm-2, the major effects of the devices include decrease of saturation drain current and increase of static drain current. The threshold voltages of GITs begin to shift slightly to the reverse direction when the neutron flux is up to 1.5×1015cm-2, which is a new effect not observed in previous results. The threshold voltage of this transistor is closely related to density of 2DEG and concentration of p-gates, and the result of shifting to the reverse direction implies that the impact of carrier removal effect to p-gate of GIT is greater than it is for 2DEG. Furthermore, experiment results have indicated that the gate current of GITs under the condition of reverse bias remain unchanged. To sum up, the work shown in this paper serves as a useful reference for studying the displacement effect of GaN power devices and their hardening.