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The temperature dependence of the 1s exciton energy has been measured in Zn1—xMgxSe epitaxial films at compositions x = 0, 0.07, 0.12, and 0.19 from 2 K up to 280 K. Detailed numerical fits of the individual temperature dependences are provided on the basis of an analytical four‐parameter representation developed recently by one of the authors. These are compared with previously used three‐parameter models of Viña et al. and Varshni. The x‐dependence of the exciton energy, E1s(T, x), and of the fundamental band gap energy, Eg(T, x), is given to very good approximation by linear functions of the composition x for any T from absolute zero up to room temperature. A comparison with recent room temperature band gap energy data by Jobst et al. shows that this linear dependence holds up to x ≈︂ 0.7. The magnitudes of the model‐dependent empirical parameters, which control the temperature dependence of the band gap energy in different compounds, are found to change significantly with increasing magnesium content. From the magnitude of the effective phonon temperature, particularly in the case of ZnSe, we conclude that the main contributions to the band gap shrinkage effect are due to acoustic phonons.

We present optical measurements of freestanding thin Znl-,Mg,Se films and of a ZnSe/Zno.g3Mgo.oj-Se single quantum well (SQW) under hydrostatic pressure applied by a diamond anvil cell. For the Znl-3 Mg,Se compounds the pressure shift of the fundamental gap was determined from absorption measurements at room temperature for z 5 0.37. A hydrostatic deformation potential a(%) = -4.85 + 0.672 eV is derived. The transition pressures Pt, to high pressure phases were determined by visual observation. The pressure dependent absorption and photoluminescence of the ZnSe SQW was investigated at 2 K. The energy shift of two SQW-related transitions was recorded and is reproduced by a simple theoretical model. LO-phonon replica were visible in photoluminescence at the sharp l l h h transition.

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)