Effect of surface passivation by SiN/SiO2 of AlGaN/GaN Heterostructures

Abstract

High electron mobility transistors (HEMT) appear as promising candidates for microwave power, radio-frequency (RF), and high temperature applications. In this thesis, we are interested in AlGaN/GaN heterostructure transistors grown on semi-insulating SiC substrates by Metal Organic Chemical-Vapour Deposition (MOCVD) and Molecular Beam Epitaxy techniques (MBE). Our objective was to identify the anomalies observed in the electrical characteristics of the transistor and to characterize the deep faults responsible for these effects. So, AlGaN/GaN/SiC HEMTs with and without passivation were investigated by Current–Voltage I V ,Transconductance-Voltage G V m  , (Conductance Deep Level Transient Spectroscopy) CDLTS and pulsed mode measurements. The current-voltage characteristics show some anomalies, such as self-heating, kink, and hysteresis effects, while the pulsed measurement reveals gate-lag and drain-lag effects. The CDLTS V measurements reveal the presence of two deep-level electron traps at 0.40eV and 0.62 eV. We have shown that these parasitic effects are linked to the deep defects existing in transistors. These trapping effects limit the performance of our structure. In order to reduce the effect of traps, a proper dielectric passivation SiO2 layer was used. We have shown that passivation improves the performance of the device.