ENVELOPE-FUNCTION FORMALISM FOR VALENCE BANDS IN WURTZITE QUANTUM-WELLS

A theoretical treatment of the valence-band spectrum of wurtzite-type materials is developed starting from the Rashba-Sheka-Pikus (RSP) 6x6 matrix Hamiltonian for coupled Gamma(9), Gamma(7), and Gamma(7) levels . A unitary transformation is applied in order to diagonalize the RSP Hamiltonian to two 3X3 blocks and the results are compared with those obtained for cubic structures [C. Y.-P. Chao and S. L. Chuang, Phys. R ev. B 46, 4110 (1992)]. Using the diagonalized form of the Hamiltonian , a solution for hole states in wurtzite quantum wells (QW's) is const ructed and explicit expressions for the QW valence subband edges are o btained. We suggest that parameters of the RSP Hamiltonian for wurtzit e structures can be deduced from experimental observations of the ener gy separation between edges of the hole subbands in QW's.