Steady-state and transient electron transport within the wide energy gap compound semiconductors gallium nitride and zinc oxide: an updated and critical review

The wide energy gap compound semiconductors, gallium nitride and zinc oxide, are widely recognized as promising materials for novel electronic and optoelectronic device applications. As informed device design requires a firm grasp of the material properties of the underlying electronic materials, the electron transport that occurs within these wide energy gap compound semiconductors has been the focus of considerable study over the years. In an effort to provide some perspective on this rapidly evolving field, in this paper we review analyzes of the electron transport within the wide energy gap compound semiconductors, gallium nitride and zinc oxide. In particular, we discuss the evolution of the field, compare and contrast results determined by different researchers, and survey the current literature. In order to narrow the scope of this review, we will primarily focus on the electron transport within bulk wurtzite gallium nitride, zinc-blende gallium nitride, and wurtzite zinc oxide. The electron transport that occurs within bulk zinc-blende gallium arsenide will also be considered, albeit primarily for bench-marking purposes. Most of our discussion will focus on results obtained from our ensemble semi-classical three-valley Monte Carlo simulations of the electron transport within these materials, our results conforming with state-of-the-art wide energy gap compound semiconductor orthodoxy. A brief tutorial on the Monte Carlo electron transport simulation approach, this approach being used to generate the results presented herein, will also be featured. Steady-state and transient electron transport results are presented. We conclude our discussion by presenting some recent developments on the electron transport within these materials. The wurtzite gallium nitride and zinc-blende gallium arsenide results, being presented in a previous review article of ours (O'Leary et al. in J Mater Sci Mater Electron 17: 87, 2006), are also presented herein for the sake of completeness.