Optical properties of HgTe-CdTe superlattices

Abstract

Optical transmittance spectra of HgTe-CdTe superlattices grown on GaAs substrates by molecular beam epitaxy were measured as a function of temperature between 40 and 360 K. Low substrate temperatures (150–170 °C) were required during growth to minimize interdiffusion and improve crystal quality. The highest quality superlattices exhibit sharp absorption edges with positive temperature coefficients in reasonable agreement with theory. In addition, many superlattices exhibit higher energy absorption features with temperature dependences similar to the lower energy fundamental absorption edge. The higher energy absorption features are associated with optical transitions involving higher order (n=2,3) superlattice minibands.