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, es pecially when compared with most III-V semiconductors such as GaAs. Ho wever, the concomitant high polar optical phonon scattering rate in Ga N tends to diminish the desirable electron transport properties. The r elationships between these two factors have been studied for the range of electric fields up to 140 kV/cm and lattice temperatures between 3 00 and 600 K. We demonstrate that in most cases electrons in GaN lose their directed average velocity over distances of only 100-200 Angstro m, and ballistic transport occurs only over such short distances. The main cause for the mall spatial scales of ballistic transport in GaN i s the strong electron-optical phonon coupling which results in rapid r elaxation of the directed electron velocity. (C) 1997 American Institu te of Physics.