Gate voltage dependence of subband structure in a two-dimensional electron gas in AlGaN/GaN heterostructures

AlGaN/GaN heterostructure devices have recently been attracting much attention because of their potential for microwave applications. Therefore, the electronic properties of a two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructures have recently been discussed. In this paper, we have studied the subbands of the 2DEG in AlGaN/GaN heterostructures by magnetoresistance measurements for the backgate voltages between 0 and -20 V up to 8 T. Since two kinds of periodic oscillations are observed, the existence of two subbands, the ground-subband and the first-excited-subband, is confirmed. The gate-voltage dependence of the electron concentration in each subband exhibits similar behaviour to the gate-voltage dependence of the electron concentration in AlGaAs/GaAs heterostructures. (C) 2002 Elsevier Science B.V. All rights reserved.