Temperature dependence of fundamental band gaps in group IV, III-V, and II-VI materials via a two-oscillator model

We perform numerical analyses of the temperature dependences of fundamental band gaps, E-g(T), and/or exciton peak positions, E-gx(T), for a large variety of group IV, III-V, and II-VI (including wide band gap) materials using a two-oscillator model. This model assumes a fixation of the low-energy oscillator in the vicinity of the dominant TA peak, whereas the location of the high-energy oscillator is taken as an adjustable parameter depending on the relative weights of the contributions of short-wavelength LA and LO/TO phonons. The material-specific sets of empirical parameters have been estimated from fittings of measured E(T) dependences. The results indicate significant changes of the relative contributions of optical versus acoustical phonons from one material to the other. The degree of dispersion is found to increase significantly with contribution of low-energy acoustical phonons. (C) 2001 American Institute of Physics.