Absorption and Photoluminescence of ZnSe/Zn_xCd_1-xSe Superlattices and Quantum Wells under Hydrostatic Pressure

Abstract

We present absorption measurements of a pseudomorphic Zn 0.75 Cd0.25 Se/ZnSe superlattice and a Zn 0 . 91 Cd0 .09 Se/ZnSe single quantum well under high hydrostatic pressure applied by a diamond anvil cell. Exci toni c transi ti ons as 1s-heavy hol e and 1s-l i ght hol e between the fi rst bound states or minibands as well as transitions in the buffer material are visible. Transition energies are well understood by calculations of the band structure near Γ. The observed energy distance between photoluminescence and hh-absorption signal gives information on exciton localization. Whereas this distance is nearly pressure independent in the buffer, there is a significant increase at pressures P > 5 GPa for quantum structures.PACS numbers: 62.50.+p, 68.65.+g, g, 42.50.-pa samples and experimental set upThe presented stuctures were grown on (001)-GaAs substrates by MBE. A Zn 0.75 Cd 0.25 Se/ZnSe superlattice (SL) (10 ZnCdSe-wells, d w = 1.4 nm, separated by ZnSe, db = 3.3 nm) was prepared on a 600 nm ZnSe-buffer. The single quantum well (SQW), dw = 10 nm, is embedded in ZnSe. It was grown on a 500 nm ZnS 0.05 Se0.95 layer, which is unstrained on GaAs. The thickness of both stuctures was kept below the critical thickness to avoid plastic relaxation. The substrate was selectively etched off by a mixture of 82% NaOH and 18% Η2O2 (30%). For high pressure measurements at 2 K we used a gasketed Syassen-Holzapfel-type diamond anvil cell (DAC) with liquid helium as pressure transmitting medium and ruby fluorescence for pressure calibration.(1017)