HOLE SCATTERING AND OPTICAL-TRANSITIONS IN WIDE-BAND-GAP NITRIDES - WURTZITE AND ZINCBLENDE STRUCTURES

The energy spectrum and transitions of valence-band carriers in wurtzi te materials are studied theoretically using cubic crystals for compar ison. We correct the commonly used cubic approximation and propose not ations for Luttinger-like parameters in wurtzite structures that simpl ify the cubic approximation to gamma(1z)=gamma(1 perpendicular to), ga mma(2z)=gamma(2 perpendicular to), and gamma(3z)=gamma(3 perpendicular to). We establish the relation between two recently proposed 3x3 matr ix blocks diagonalizing the full 6x6 Hamiltonian and provide geometric interpretation in three-dimensional Bloch space. The formalism is use d then to derive transition matrix elements for three types of process es: (i) macrofield hole scattering, described by the Bloch overlap fac tor; (ii) optical transitions between conduction and valence bands; an d (iii) intervalence band optical transitions. Finally, we discuss the set of material parameters for group-III nitrides and present the num erical results.