Absorption of Thin ZnSe, ZnS and ZnS_xSe_1-xFilms under High Hydrostatic Pressure

Abstract

We present absorption measurements on free-standing ZnSe, ZnS and Z n S x S e 1 -x f i l m s Samples and experimental setupCubic samples were grown by metalorganic vapour phase epitaxy (MOVPE) or MBE on (001)-orientated GaAs. The substrate was removed in two steps. First, the .GaAs was mechanically polished to a thickness of about 50 μm, then the remaining GaAs was etched off selectively by a 82% n-ΝaOΗ and 18% Η2O2 (30%) mixture. The investigations under hydrostatic pressure have been performed in a gasketed diamond anvil cell (DAC) with liquid He as pressure transmitting medium. Ruby fluorescence was used for pressure calibration. Results and discussion Pressure dependence of the refractive index of ZnSe, ZnSThe refractive index n(λ, P) was measured by analyzing the interference pattern of MOVPE-samples with plane-parallel surfaces (thickness 2 μm). The maxima and minima in the transparent region (α = 0) are given by where d is the sample thickness, m -the order of the interference and λ -the wavelengths of the interference extrema. At P = 0 we used well known curves of 'This work was supported by Deutsche Forschungsgemeinschaft (DRG).(995)

Absorption and Photoluminescence of ZnSe/ZnxCd1-xSe Superlattices and Quantum Wells under Hydrostatic Pressure

“…The calculations fit well to both experimental data sets and to a Zn 0.82 Cd0.18Se/ZnSe SL, presented in Ref. [9], but it is not very sensitive to variation of the band offset. Some parameters of cubic CdSe were not available and had to be extrapolated (see Table).…”

“…Electronic transitions have excitonic character. An increase in the excitonic binding energy R under pressure is caused by a change of the effective masses and the dielectric constant εstat [7]. Furthermore the confinement changes under pressure.…”

Zn1−xMgxSe Samples and a ZnSe/Zn0.93Mg0.07Se Quantum Well under Pressure: Optical Absorption and Photoluminescence

“…1, see inset). This is in contrast to ZnSe which undergoes a first order phase transition from zincblende to the NaCl structure [7] and becomes opaque for visible light [8].…”

Deformation Potentials

“…Therefore, the linearly interpolated a, b and d values for Ga x In 1Àx P y As 1Ày /InP using Equation (A.6) are plotted in Figure 8.9(a). The solid circles represent the experimental data obtained from the pressure coefficients dE 0 /dp ( Figure 6.46(b)) using the same procedure as in The pressure coefficient dE 0 /dp has been measured on some II-VI semiconductor alloys, such as w-Mg x Zn 1Àx O [21], w-Zn x Cd 1Àx S [22], c-ZnO x Se 1Àx [23], ZnS x Se 1Àx [24], ZnS x Te 1Àx [25] and ZnSe x Te 1Àx [26]. Figure 8.9(b) shows the E 0 -gap DP a G 0 versus y for Ga x In 1Àx P y As 1Ày /InP.…”