THE EFFECT OF PRESSURE ON THE LUMINESCENCE FROM GAAS/ALGAAS QUANTUM-WELLS

Photoluminescence (PL) from GaAs quantum wells with widths from 50 Angstrom to 300 Angstrom and AlxGa(1-x)As barriers (x = 0.3 and 1) was studied under pressure up to 35 kbar at two temperatures (300 K and 77 K). We used (and compared) three types of pressure devices: gas cells, liquid cells and the diamond-anvil cell. Accurate values for the pressure variation of the pi energy were obtained. They reveal the small dependence on the parameters of the well, in agreement with the envelope-function calculation. Pressure shift of the PL lines is the same at 77 K and at 300 K. In several samples we found the change of the pressure coefficient of the direct (Gamma) line at the Gamma-X crossover pressure. We interpret this as the resonance effect due to the mixing of the Gamma state in the well with the X continuum in the barriers. This means that the pressure dependence of the quantum-well lines should not be fitted with a single curve below and above the Gamma-X crossover pressure. From our results we obtain the linear pressure coefficient of the GaAs energy gap equal to 11.6 meV kbar(-1). The deformation potential of the gap seems to be almost independent of pressure up to 15 kbar.