Enhancement-mode AlN/GaN MOSHEMTs fabricated by selective area regrowth of AlGaN barrier layer

Enhancement-mode (E-mode) metal-oxide semiconductor high electron mobility transistors (MOSHEMTs) have been fabricated by selective area regrowth technique on AlN/GaN heterostructure. A selectively regrown AlGaN barrier layer could effectively increase the 2-dimensional electron gas (2DEG) density underneath. In comparison with the conventional methods of plasma etching/treatment in the gate region, the regrowth technique can effectively avoid damage caused by the plasma process. Atomic layer deposition of Al₂O₃ was employed as the gate dielectric. It was found that the Al₂O₃ on the AlN barrier layer also could induce a higher density of 2DEG. The fabricated E-mode MOSHEMTs with a 1.4-μm gate length exhibited excellent performance of maximum drain current of 530 mA/mm and peak transconductance of 310 mS/mm. The threshold voltage of MOSHEMTs was around +0.2 V. The reverse leakage current was also observed to be around 3.6 × 10^-4 mA/mm at V_gs = -1 V and V_ds = 6 V. The peak channel electron mobility was extracted to be 880 cm²/Vs using split-CV method. These results indicate that the regrowth technique is a promising method to realize E-mode transistors.