Analysis of effects of interface-state charges on the electrical characteristics in GaAs/GaN heterojunctions

Electrical properties of p(+)-GaAs/n-GaN and n+-GaAs/n-GaN junctions fabricated by surface-activated bonding are investigated by measuring their capacitance-voltage (C-V) and current-voltage (I-V) characteristics. The difference between their flat-band voltages (0.17 eV), which are extracted from C-V measurements, disagrees with the ideal value (1.52 V), suggesting that the Fermi level should be pinned at the bonding interface. The C-V characteristics of the two junctions are calculated by assuming that the Fermi level is pinned at the interface. The measured C-V characteristics quantitatively agree with modeled ones obtained by assuming that the interface state density and conduction band discontinuity are 1.5 x 10(14) cm(-2) eV(-1) and 0.63 eV, respectively. The effective heights of barriers at interfaces, which we estimate by analyzing dependences of I-V characteristics on the ambient temperature, are > 10-20 meV for the two junctions at room temperature. This suggests that the transport of carriers is dominated by tunneling through interface states. (C) 2018 The Japan Society of Applied Physics