Analysis of AlGaN/GaN high electron mobility transistors with nonalloyed Ohmic contacts achieved by selective area growth using plasma assisted molecular beam epitaxy

We achieved low-resistance nonalloyed Ohmic contacts for n-type GaN using selective area growth (SAG) by plasma assisted molecular beam epitaxy (PAMBE). Thus-fabricated high electron mobility transistor (HEMT) demonstrated comparable or more favorable electrical performance than the conventional alloyed counterpart. Meanwhile, the nonalloyed PAMBE-SAG technique avoids problems created by the high temperature annealing, such as the lateral diffusion of contact metals and the generation of surface defects. Consequently, ultrafine electrodes are realized for device downscaling, defect-induced current degradation is alleviated, the reliability and uniformity of HEMTs are improved.