Optical characterization of strained InxGa1− xAs− Al0.28Ga0.72As heterostructures grown by molecular beam epitaxy

Abstract

Low temperature photoluminescence measurements were carried out on pseudomorphically strained In x Ga 1- x As− Al 0.28 Ga 0.72As ternary-on-ternary heterostructures grown by molecular beam epitaxy to investigate the change in the transition energy and linewidth as a function of InGaAs well thickness at two different indium compositions x = 0.10 and x = 0.15, respectively. Sharp excition 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 increases up to 300 Å. In addition, there are signs of linewidth broadening at higher well thicknesses which may indicate the onset of plastic relaxation. Relatively small variations in the transition energy were observed at well thicknesses which were above the theoretical critical thickness value as calculated by the Matthews-Blakeslee model [J. Crystal Growth 27 (1974) 118], suggesting the existence of a second value, higher than the theoretical critical thickness value. Good agreement between experimental and calculated transition energy versus well thickness data was obtained, from which the conduction band offset Δ E c/Δ E g was estimated to be 0.65±0.05 for x = 0.10−0.15, consistent with the results derived from other techniques.