Pressure and temperature dependence of the band-gap in CdTe

In this paper we report on isothermal compression measurements (up to 5 GPa and 500 K) of the optical absorption edge of 1 mum epitaxial layers of CdTe growth by metalorganic chemical vapor deposition (MOCVD) on GaS substrates. The isothermal blue shift under pressure of the direct energy gap (Gamma(15)(v) --> Gamma(1)(c)) in the zinc-blende phase is about 7.1 x 10(-2) eV GPa(-1) and is found to be independent of temperature within the experimental errors. The isobaric red shift in the stability range of the zinc-blende phase is about -3.76 x 10(-4) eV K-1. Regarding the phase transitions, no discontinuity in the energy gap has been found in the narrow pressure range where the cinnabar phase can be present. The transition pressure to the NaCl-type structure in CdTe is found to decrease with increasing temperature (294-500 K) following the law P-t = 4.1 GPa - 6.6 x 10(-3) (T - 273) (K).