Effects of surface treatment on the velocity-field characteristics of AlGaN/GaN heterostructures

AlGaN/GaN test structures were fabricated with an etched constriction. A nitrogen plasma treatment was used to remove the,disordered layer, including natural oxides on the AlGaN surface, before the growth of the silicon nitride passivation film on several of the test structures. A pulsed voltage input, with a 200 ns pulse width, and a four-point measurement were used in a 50 Omega environment to determine the room temperature velocity-field characteristic of the structures. The samples performed similarly over low fields, giving a low-field mobility of 545 cm(2) V-1 s(-1). The surface treated sample performed slightly better at higher fields than the untreated sample. The highest velocity measured was 1.25 x 10(7) cm s(-1) at a field of 26 kV cm(-1).