Processing Methods for Low Ohmic Contact Resistance in AlN/GaN MOSHEMTs

In this work, we demonstrate various ohmic contact forma-tion processes using an AlN/GaN (MOS)HEMT structure with an aluminum oxide gate dielectric formed by ALD. The MO-SHEMT structure is advantageous because the thin oxide layer protects the ultra-thin (~3 nm) AlN barrier against exposure to the processing chemicals. Contact resistance values as low as 0.457 Ω·mm are reported on TLM structures. The correspond-ing devices exhibited excellent electronic transport properties with room temperature mobility µ> 1000 cm2/V·s and sheet carrier concentration nS> 3.25 x 1013 cm-2. These are the low-est contact resistance values obtained for AlN/GaN HEMTs in the high mobility range (> 1000 cm2/V·s)