The Effect of Ohmic Contact Location on the Buffer Leakage Current of AlGaN/GaN Heterostructure

The effect of ohmic contact location on the buffer leakage current of AlGaN/GaN heterostructure was investigated and the AlGaN/GaN HEMT employing the proposed ohmic contact pattern was fabricated. We have fabricated 3 different types of ohmic patterns; type A - both contacts are on the etched GaN buffer layer, type B - one is on the etched GaN buffer layer and the other is on the unetched GaN cap layer and type C - both contacts are on the unetched GaN cap layer. Our experimental results showed that the ohmic contact on GaN buffer increased the buffer leakage current due to the lateral diffusion of ohmic metals. The proposed AlGaN/GaN HEMT successfully decreased the leakage current and did not affect the forward drain current and the transconductance.