Characteristics of Al2O3/AllnN/GaN MOSHEMT

InAlN/GaN is a new heterostructure system for HEMTs with thin barrier layers and high channel current densities well above 1 A/mm. To improve the leakage characteristics of such thin-barrier devices, AllnN/GaN MOSHEMT devices with a 11 nm InAlN barrier and an additional 5 nm Al2O3 barrier (deposited by ALD) were fabricated and evaluated. Gate leakage in reverse direction could be reduced by one order of magnitude and the forward gate voltage swing increased to 4 V without gate breakdown. Compared to HEMT devices of similar geometry, no degradation of the current gain cutoff frequency was observed. The results showed that InAIN/GaN FETs with high channel current densities can be realised with low gate leakage characteristics and high structural aspect ratio by insertion of a thin Al2O3 gate dielectric layer.