OPTICAL-PROPERTIES OF CDTE/CD1-XZNXTE QUANTUM-WELLS AND SUPERLATTICES

MBE growth of high-quality CdTe/Cd1-xZnxTe single quantum wells and superlattices with x=0.08-0.15, on Cd0.96Zn0.04Te substrates, is described. Due to lattice-parameter mismatch, the different layers are strained, and these strains predominate in determining the valence-band discontinuity at the CdTe/Cd1-xZnxTe interfaces. Deformation potentials for CdTe are determined from optical spectra of strained CdTe layers. Optical properties of excitons in single quantum wells are described, emphasizing methods for identifying the different transitions (optical pumping experiments) and the nature of the quantized exciton states observed (centre-of-mass quantization versus separate-carrier quantization). Oscillator strengths for excitons in CdTe layers and quantum wells are determined as a function of layer thickness from transmission measurements. A high quality superlattice shows both direct (Type I) heavy-hole and indirect (Type II) light-hole exciton transitions; for this sample the 2s excited state of the heavy exciton is identified by its diamagnetic shift and the band offsets are deduced directly from the energies of direct and indirect transitions. © 1989.