Ti/Al/Ti/Au and V/Al/V/Au contacts to plasma-etched n-Al _0.58Ga _0.42N

Cross-sectional transmission electron microscopy was used to study annealed Ti/Al/Ti/Au and V/Al/V/Au ohmic contacts to as-received and plasma-etched n-Al _0.58Ga _0.42N. The reaction depth of low-resistance V-based contacts to as-received n-Al _0.58Ga _0.42N is very limited, unlike previously reported Ti-based contacts to n-Al _x Ga _1-x N. In the present study, the Ti/Al/Ti/Au contacts to as-received n-Al _0.58Ga _0.42N required much higher annealing temperatures than the V-based contacts and also exhibited deeper reactions on the order of 40 nm. To achieve a low contact resistance on plasma-etched n-Al _0.58Ga _0.42N, different metal layer thicknesses and processing conditions were required. The Ti- and V-based contacts to plasma-etched n-Al _0.58Ga _0.42N exhibited both similar contact resistances and limited reaction depths, along with the presence of an aluminum nitride layer at the metallization/semiconductor interface. Metal channels penetrate the aluminum nitride layer connecting the top of the metallization to the n-Al _0.58Ga _0.42N. The similarity in phase formation in the contacts to plasma-etched n-Al _0.58Ga _0.42N is likely the reason behind the similarity in specific contact resistances.