A photoluminescence study of the effect of well thickness in strained InGaAs/AlGaAs heterostructures grown by molecular beam epitaxy

Abstract

Low temperature photoluminescence measurements were carried out on pseudomorphically strained InxGa1−xAs-Al0.28Ga0.72As ternary-on-ternary heterostructures grown by molecular beam epitaxy to investigate the change in the transition energy, linewidth, and intensity as a function of InGaAs well thickness at two different indium compositions, x = 0.10 and x = 0.15, respectively. Sharp exciton peaks as narrow as 4-6 meV were observed from the InGaAs wells grown at 530 °C with 1 min of growth interruption at the top and bottom heterointerfaces. The linewidth decreases as the well thickness is increased up to 300 Å. In addition, there are signs of linewidth broadening and sharp decrease in the photoluminescence intensity at higher well thicknesses that may indicate the onset of plastic relaxation. Relatively small variations in the transition energy were observed at well thicknesses that are up to ≍3 times the theoretical critical layer thickness calculated by the Matthews-Blakeslee model,10 suggesting that the small density of dislocations that may be present may not have a significant effect on the band structure of the well.