Growth in one operation of the (Cd, Hg)Te alloys of all compositions to study the alloy disorder

Abstract

A complete series of compositions of high purity Hg x Cd 1- x Te are obtaind by a single THM pass involving a particular arrangement, in order to ensure only a small change in the nature and concentration with x of residual impurities. Binding energies of shallow donors and free excitons are measured at low temperature by photoluminescence experiments on dilute Cd-rich alloys, and the inhomogeneous broadening is determined from the shape of the off-resonance Electronic Raman Scattering signal. It is shown that the effective mass description of donor levels breaks down at low Hg concentration whereas no anomaly is observed in the case of free excitons. A deviation from a random distribution of atoms, at least in the vicinity of donors, is invoked.