Transient ballistic transport in GaN

Monte Carlo simulations have been used to study the spatial scales of electron ballistic transport in GaN. The large optical phonon energy (92 meV) and the large intervalley energy separation between the Gamma and satellite conduction band valleys (greater than or equal to 1.5 eV) suggest an increasing role for ballistic electron effects in GaN, especially when compared with most III-V semiconductors such as GaAs. However, the concomitant high polar optical phonon scattering rate in GaN tends to diminish the desirable electron transport properties. The relationships between these two factors have been studied for the range of electric fields up to 140 kV/cm and lattice temperatures between 300 and 600 K. We demonstrate that in most cases electrons in GaN lose their directed average velocity over distances of only 100-200 Angstrom, and ballistic transport occurs only over such short distances. The main cause for the mall spatial scales of ballistic transport in GaN is the strong electron-optical phonon coupling which results in rapid relaxation of the directed electron velocity. (C) 1997 American Institute of Physics.