Interband transition physics from the absorption edge in GaN: New prospects from numerical analysis

The strong polarization effects and abundant surface states in III-nitrides result in a tunable electric field, modifying the absorption/emission by changing the band structure. Thus, the mechanism of the electric field and the absorption/emission is crucial for future optical logic devices. Here, we propose to extract the information from the absorption/emission edge by numerical simulations. The simulations show that the increase in the field strength would red-shift the spectrum as well as decrease the slope of the edge for both the uniform and non-uniform field. For numerical simulations, we also provide the lower limit of the quantum states to be simulated from Wentzel–Kramers–Brillouin approximation. Then three GaN samples with different n values are analyzed, and the results validate our methods in two ways. On the one hand, the nonuniform field is shown to fit the experimental absorption better at higher n, which is in accordance with previous studies. On the other hand, the reasonable bandgap Eg at zero doping level and the bandgap-renormalization coefficient are obtained. This work would deepen the understanding of the absorption/emission influenced by the electric field and pave the way for numerical analysis of the edge.