I–V and C–V characteristics and interface electron states of Al₂O₃/AlGaN/GaN structures

This paper analyzes properties of the dielectric/AlGaN/GaN system with an ALD Al₂O₃ film as a dielectric. It was investigated how the current flow process in the system changes due to the deposition of films with different thicknesses; at what bias voltage the electron emission process from the boundary states begins, and how the properties of the barrier layer in the initial heterostructure affect the parameters of the current in the system. It was found that a positive charge forms at the Al₂O₃/AlGaN interface, the charge magnitude increasing with the film thickness. It was also shown that film deposition affects the charge magnitude in the channel. It was demonstrated that the frequency at which C–V measurements are carried out affects D_it, i.e., the distribution of the electron states at the boundaries of the Al₂O₃/AlGaN/GaN system. It was shown that the density of the detected donor-like states increases abruptly with an increase in the measurement frequency. It was furthermore demonstrated that a correctly chosen measurement scheme allows one to estimate the potential contribution of the two boundaries, i.e., AlGaN/GaN and Al₂О₃/AlGaN, in this case, some of the electrons may remain in the channel.