TEMPERATURE-DEPENDENCE OF THE BAND-GAP OF CD1-XZNXTE ALLOYS OF LOW ZINC CONCENTRATIONS

The temperature dependence of the fundamental band-gap E(0) of Cd1-xZn xTe alloys with zinc concentrations in the 0 to 0.3 range has been det ermined by modulated photoreflectance (PR). E(0) is found to vary from 1.511 eV for x=0.00 to 1.667+/-0.008 eV for x=0.3, at room temperatur e and from 1.602 eV at x=0.00 to 1.762+/-0.004 eV for x=0.3 at 10 K. T he measured broadening parameters Gamma have values between 25 and 45 meV at room temperature and decrease monotonically to values around 5 meV or smaller at 10 K. The temperature dependence of the observed ban d gap energies is well described by the well known Varshni formula E(T ) = E(0)-AT(2)/(T+theta) for all samples studied. The PR temperature b roadening is well understood assuming that it results from the scatter ing of the excitonic electron-hole pair responsible of the band-to-ban d transition PR signal off LO phonons. (C) 1996 American Institute of Physics.