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

Photoluminescence (PL) from GaAs quantum wells with widths from 50 Ang strom to 300 Angstrom and AlxGa(1-x)As barriers (x = 0.3 and 1) was st udied 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 press ure variation of the pi energy were obtained. They reveal the small de pendence on the parameters of the well, in agreement with the envelope -function calculation. Pressure shift of the PL lines is the same at 7 7 K and at 300 K. In several samples we found the change of the pressu re coefficient of the direct (Gamma) line at the Gamma-X crossover pre ssure. 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 n ot 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 pot ential of the gap seems to be almost independent of pressure up to 15 kbar.