OPTICAL STUDIES OF STRAINED INGAAS/GAAS SINGLE QUANTUM-WELLS

Photoluminescence and absorption experiments on strained In0.20Ga0.80As/GaAs single quantum well (SQW) structures are reported as a function of the GaAs capping layer thickness which ranges from 5 to 500 nm. The luminescence peak is shifted to lower energy as the GaAs capping layer thickness decreases, which is the first demonstration of the effect of the GaAs capping layer thickness on the strain of InGaAs/GaAs single quantum wells. Excitonic transitions up to the recombination between the fourth electron subband and the fourth hole subband (4e-4hh), both allowed and forbidden, are observed in the absorption spectra. The strain of each sample has been deduced. The calculated results, taking into account both the strain and the quantum well effect, are in good agreement with the measured values. The minimum GaAs capping layer thickness for the growth of strained In0.20Ga0.80As(25 nm)/GaAs SQW structures is estimated to be 5-10 nm.