Effect of Ar ion beam channeling on AlGaN/GaN heterostructures during the ion beam etching process

The effect of Ar+ ion beam etching of AlGaN/GaN heterostructures at a bias voltage of 250 V was investigated with respect to different ion incident an gles. The samples were measured before and after etching with respect to mo bility, sheet electron concentration, and sheet resistance. We found a pron ounced dependency of the electrical characteristics after etching on the io n incident angle. Especially at zero degree, the mobility of the two-dimens ional electron gas (2DEG), which is located at the AlGaN/GaN interface, dec reases dramatically after etching. The sheet resistance increases in the sa me way. At larger ion incidence angles, the effect vanished. We attribute t his behavior predominantly to channeling of the ions through the AlGaN laye r down to the 2DEG. An annealing step after etching shows improvement of th e electrical characteristic. These results show that gate-recessed GaN fiel d effect transistors can be limited in their device performance by etch-pro cess-induced ion channeling effects. The results also show how etch-induced defects in the gate recess step can minimized. (C) 2000 American Institute of Physics. [S0003-6951(00)04514-9].