Optical Characterization of High Quality ZnTe Substrate

Abstract

The photoluminescence (PL), optical reflectance, optical transmittance and piezoelectric photothermal spectra were successfully observed between liquid helium and room temperatures for high quality p-type P-doped ZnTe substrates. In the PL spectrum of the ZnTe substrate (1 Â 10 18 cm --3 ), three distinct kinds of peaks which were due to the radiative recombination of the exciton bound to a neutral acceptor (I 1 ) and free to a neutral acceptor (FA) with longitudinal optical phonon replicas were present at liquid helium temperature. The bandgap energy was estimated to be 2.394 eV by adding the reflection peak (2.381 eV) to the exciton binding energy. Furthermore, the activation energy of the phosphor acceptor impurity was estimated to be 65 meV. On the other hand, in the higher carrier concentration substrate (8 Â 10 18 cm --3 ), the PL intensity was much smaller than in that of the lower carrier concentration substrate. This means that radiative recombination processes decrease with increasing carrier concentrations.