PRESSURE TUNING OF STRAIN IN CDTE INSB EPILAYER - A PHOTOLUMINESCENCEAND PHOTOMODULATED REFLECTIVITY STUDY/

The heavy-hole and light-hole excitons of a CdTe epilayer, pseudomorph ically grown on an InSb epilayer by molecular beam epitaxy, are studie d with a diamond anvil cell as a function of applied hydrostatic press ure via photoluminescence (PL) and photomodulated reflectivity (PR) sp ectroscopies. They are compared with the excitonic features in the sim ultaneously measured PL spectra of a sample of bulk CdTe. Under applie d pressure, the lattice mismatch-induced splitting between the light-h ole and heavy-hole related transitions increases in a continuous and r eversible manner because of the additional pressure-induced compressio n due to the difference in the compressibilities of CdTe and InSb. The unusually large strain sustained by the CdTe epilayer under pressure is discussed in the light of various models. The PR signal vanishes af ter the InSb epilayer goes through a structural phase transition at ap proximately 20 kbar, while the PL signal persists until it is irrevers ibly quenched by the CdTe epilayer undergoing a structural phase trans ition at approximately 30 kbar. For pressures between 20 and 30 kbar, the behavior of the CdTe epilayer is similar to that of the bulk sampl e; the strain appears to have been relaxed due to the structural phase transition which has taken place in InSb. Values of the first- and se cond-order pressure coefficients for bulk CdTe and for the CdTe epilay er as well as values of the hydrostatic and shear deformation potentia ls are obtained at 14 and 80 K and compared with previously quoted val ues.