High-field properties of carrier transport in bulk wurtzite GaN: A Monte Carlo perspective

The transport properties of both electron and hole in bulk wurtzite phase GaN in the high electric field domain are presented by using an ensemble Monte Carlo (EMC) method. In our EMC simulation, the impact ionization process, which is seldom studied due to the lack of experimental data, is included. The impact ionization is treated as an additional scattering mechanism, and the impact ionization rate is described by the Keldysh formula, with the parameters in the formula determined by fitting the simulation results to the numerical calculation results. Such a treatment makes it convenient to simulate the impact ionization initiated by either an electron or hole with the EMC method compared to the previous study of carrier transport properties in GaN up to the high field. Steady-state properties of carriers under an applied electric field up to 1 MV/cm are presented and analyzed. Particularly, the impact ionization process here is further studied and detailed discussions are also given. It is found that the impact ionization coefficients of both the electron and hole upon applied electric field can be described by two simple experiential equations. Moreover, for the first time, to the best of our knowledge, we obtain the ratio of the electron impact ionization coefficient to the hole impact ionization coefficient in wurtzite GaN and find out that it can be smaller than that in InP, which means wurtzite GaN may have good gain noise behaviors according to the present noise theories.