| Scope and method of study. Optical properties of strained heterostructures in III-V and II-VI compounds have been investigated using various optical spectroscopic techniques, such as photoluminescence, photoluminescence excitation, photoreflectance, and photomodulated transmission measurements. Hydrostatic pressure, using a diamond anvil high-pressure cell, has been applied to study the pressure dependence of PL.; Findings and conclusions. Pressure induced {dollar}Gamma{dollar}-X band crossover has been observed at pressures around 26 kbar in a GaAs/GaAs{dollar}rmsb{lcub}0.68{rcub}Psb{lcub}0.32{rcub}{dollar} strained multiple quantum well (SMQW) sample. With this crossover, the valence band offset ratio in the heterojunction has been determined to be {dollar}Qsb{lcub}v{rcub} = 0.25.{dollar} The pressure induced band crossing in other GaAs/GaAs{dollar}sb{lcub}1-x{rcub}{lcub}rm P{rcub}sb{lcub}x{rcub}{dollar} samples was impossible to observe due to a donor-like deep level, which appeared at pressures higher than 17 kbar. The comparison of the experimental results and theoretical calculations showed that the coupling between the light-hole and the split-off band must be included to fit the higher order ({dollar}n ge 2){dollar} interband transitions in InAs{dollar}sb{lcub}1 - x{rcub}{lcub}rm P{rcub}sb{lcub}x{rcub}{dollar}/InP SMQW's. From the pressure dependent PL results and the ambient pressure PL and PLE spectra, the critical thickness of the CdSe well layer in highly strained CdSe/ZnSe single quantum wells was estimated as less than 4-monolayers which agreed well to the theoretically calculated value. The oscillations in PLE spectra in ZnSe/CdSe single quantum wells (SQW's) are attributed to the Franz-Keldysh effect due to the built-in electric field in the SQW's. The origin of the field is not yet understood. For the first time, pressure dependent PL of cubic GaN has been studied. Pressure coefficients of various transitions have been determined. |
