Modulated interfacial band alignment of β-Ga2O3/GaN heterojunction by the polarization charge transfer

[Display omitted] •N- and Ga-terminated GaN surfaces possess opposite band bends induced by polarization.•2DEG is just found at N-terminated β-Ga2O3/GaN heterojunction in theory.•Both 2DEG and interfacial energy barrier are observed for N-terminated heterojunction.•All Ga-terminated β-Ga2O3/GaN heterojunctions possess 2DEG coupling with gap states.•O-dopant at the GaN region can turn the energy barrier into energy groove with 2EDG. Designing β-Ga2O3/GaN heterojunction has been regarded as a promising approach to optimize the application of β-Ga2O3. Here, band characters of β-Ga2O3/GaN heterojunction are deeply understood by the polarization effect of GaN, which is vital to design high-performance β-Ga2O3/GaN heterojunction. Due to the inconsistent band bending and orbital distribution induced by GaN polarization effect, just N-terminated β-Ga2O3/GaN heterojunction theoretically shows the type-II band alignment with two-dimensional electron gases (2DEGs). Such 2DEGs are just actually observed for N-terminated β-Ga2O3/GaN heterojunctions with weak interfacial interaction, but obvious interfacial energy barriers are found for heterojunctions with strong interfacial interactions which can weak the polarization charge transfer. The interfacial energy barriers can be turned into energy grooves upon introducing O-dopant with low concentration into the GaN region of heterojunction. In addition, all Ga-terminated β-Ga2O3/GaN heterojunctions possess 2DEG band alignments, but abundant interfacial gap states are observed due to the lost electron of Ga atom from β-Ga2O3 region and accumulated polarization electron of N atom from GaN region. In addition, band bending characters of β-Ga2O3/GaN heterojunctions are negligibly dependent of the atomic arrangements of β-Ga2O3 and GaN surfaces. These works deeply understand the interfacial performances of β-Ga2O3/GaN heterojunctions and provide useful guidance for realizing high-performance β-Ga2O3/GaN heterojunctions.