BAND-TO-BAND TRANSITIONS AND FREE-EXCITON STATES IN LOW-SYMMETRY CRYSTALLINE GATE

In this paper we derived the selection rules for band-to-band transiti ons in low-symmetry crystalline GaTe and explained the low-temperature (2 K) absorption spectra at two different polarization configurations for this material. It is found that the top two valence bands of crys talline GaTe at the high symmetry Gamma-point have one-dimensional deg eneracy and are weakly separated (< 0.5 meV). From this band structure , we re-analyzed the free exciton states in crystalline GaTe and found that the X(1) peak is composed of the heavy-hole (HH) and light-hole (LH) singlet excitons, while the X(2) peak is composed of the HH and L H triplet excitons. (C) 1997 Elsevier Science Ltd.