RAMAN AND MODULATED-REFLECTIVITY SPECTRA OF A STRAINED PSEUDOMORPHIC ZNTE EPILAYER ON INAS UNDER PRESSURE

The piezomodulated-, electromodulated-, and photomodulated-reflectivit y spectra of a pseudomorphic ZnTe epilayer, grown on an InAs epilayer by molecular-beam epitaxy, exhibit heavy- and light-hole excitonic sig natures split by the lattice mismatch induced biaxial compressive stra in. This splitting in the pseudomorphic epilayer is studied as a funct ion of applied hydrostatic pressure using photomodulated reflectance s pectroscopy at 80 K. With increasing hydrostatic compression, the comp ressive strain is progressively compensated by the pressure-induced te nsile strain. At similar to 55 kbars the epilayer becomes strain-free, and is under a biaxial tension at higher pressures. The separation be tween the heavy- and light-hole signatures is superlinear in pressure, suggestive of a strain or volume deformation-dependent shear deformat ion-potential constant. We also compare the pressure dependence of she Raman LO phonon of the ZnTe epilayer on InAs with that of a bulk ZnTe sample at 13 K. The pressure-dependent strain is found to be linear. Accurate values of the first-order strain derivatives of the LO phonon s and mode Gruneisen constants are obtained.