IDENTIFICATION OF VALENCE SUBBANDS IN CDTE-CD1-XZNX TE STRAINED-LAYER QUANTUM-WELLS BY DIFFERENTIAL SPECTROSCOPY

Wavelength-modulated reflectivity and piezomodulated reflectivity investigations have been made at 6 K on a series of CdTe-Cd1-xZnxTe (x0.08 and 0.13) strained-layer single quantum wells grown on Cd1-yZnyTe substrates (y0.04). The reflectivity patterns exhibit a rich series of structures which are unambiguously identified in terms of 3/2;± 3) / 2 (heavy-hole) or 3/2;±1/2 (light-hole) excitons. Comparison between wavelength-modulated and piezomodulated data enables us to identify the quantum-well-related transitions as transitions of type-I nature between ground and excited conduction and heavy-hole valence subbands. This has been obtained for a series of quantum-well widths ranging from 50 up to 450. Our findings are consistent with a small value of the CdTe-ZnTe zero-strain valence-band offset. The calculated light-hole-related transitions, which we did not observe in reflectivity when x0.08 but were detected when x0.13, are then found to have a type-II nature. © 1990 The American Physical Society.