The effect of pressure on the luminescence from GaAs/AlGaAs quantum wells

Photoluminescence (PL) from GaAs quantum wells with widths from 50 AA to 300 AA and Al x Ga 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 PL energy were obtained. They reveal the small dependence on the parameters of the well, in agreement with the envelope-function calculation. Pressure shifts 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.