INVESTIGATION OF THE CONDUCTION BAND-STRUCTURE IN (001) ORIENTED TYPE-II GAAS ALAS SHORT-PERIOD SUPERLATTICES USING (100) UNIAXIAL-STRESS/

We present an investigation of the effects of uniaxial stress on the c onduction band alignment of type II GaAs/AlAs short period superlattic es using photoluminescence (PL) spectroscopy. in the absence of pressu re, the conduction band ground state derives from the longitudinal X s tates in the AlAs layers, whereas at higher pressures the transverse X states shift to a lower energy. This crossing is clearly visible in t he PL, and the shift in the transition energies is used to determine a value for the tetragonal shear deformation potential of the X point o f AlAs, Xi(t)(X), of 6.9 +/- 0.6 eV. This is compared with existing es timates, and is used to confirm a value of 23 meV as the ambient press ure strain dependent splitting between the longitudinal and transverse X states. The ambient pressure confinement splitting is then investig ated by using a linear extrapolation of the pressure shift in the tran sverse X features. This leads to the first estimation of the zero pres sure state alignment from samples having a conduction band ground stat e of longitudinal X character, along with large confinement energies. Comparisons with the Kronig-Penney model suggest that the current valu e of the transverse effective mass of AlAs may need to be reassessed.