Novel E-Mode GaN-on-Si MOSHEMT Using a Selective Thermal Oxidation

A novel normally-off AIN/GaN metal-oxide-semiconductor high electron mobility transistors (MOSHEMT) on 100-mm Si substrates for high-power applications is demonstrated for the first time by means of a selective thermal oxidation of AIN. The formation of a high-quality insulating AION layer resulting from the dry thermal oxidation of AIN at 900 degrees C in oxygen has been identified by transmission electron microscopy and X-ray photoelectron spectroscopy. The AIN thermal oxidation appears to be highly selective toward the SiN cap layer allowing the local depletion of the 2-D electron gas ( self-aligned to the gate) and thus the achievement of normally-off operation. Threshold voltage (V-T) of +0.8 V and drain leakage current at V-GS = 0 V well below 1 mu A/mm are obtained reproducibly over the wafer. The comparison of the fabricated MOSHEMTs with the control sample (identical but nonoxidized) reveals a drastic shift of V-T toward positive values and three to four orders of magnitude drain leakage current reduction.