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 Vgs = -1 V and Vds = 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.