STRAIN EFFECTS IN CHEMICALLY LIFTED GAAS THIN-FILMS

The optical absorption of strained, chemically lifted GaAs films was measured. The films were grown by molecular-beam epitaxy, and then were chemically released from their substrates using a preferential etch and were glued to a quartz plate. Because of the differential thermal expansion of GaAs and quartz, the semiconductor film is under tension below room temperature. From the optical absorption of the film between 10 and 160 K, the hydrostatic and uniaxial deformation potentials were found to be a=-7.6+0.6 meV and b=-1.92+0.04 meV, respectively. Very narrow excitonic linewidths were observed at low temperatures, but the exciton-phonon coupling was found to be the same as for an unstrained, bulk GaAs film. The spin-orbit splitting 0 was found to be independent of temperature between 20 K and room temperature. © 1990 The American Physical Society.