Layer perfection in ultrathin MOVPE-grown InAs Layers buried in GaAs(001) studied by X-ray standing waves and photoluminescence spectroscopy

摘要

Using the In-L fluorescence produced by normal-incidence X-ray standing waves, we have measured the layer perfection and positions of 1 and 1/2 monolayer (ML)InAs quantum wells buried in GaAs(001). Growth temperature effects were studied in a series of samples produced by metalorganic vapor phase epitaxy (MOVPE) at temperatures between 400 and 600 deg C. The coherent position of the In atoms decreases with temperature in the 1 ML samples, and the optimal growth temperature is near 550 deg C, as evidenced by the coherent position of 1.15+-0.02 and the relatively high coherent fraction of 0.72+-0.08. These results are corroborated by 1.6 K photoluminescence (PL) measurements in which the most sharp and intense In-excitonic emission is obtained from a sample grown at 530 deg C. For the 1/2 ML samples, growth temperatures of 400 deg C and 600 deg C produces similar standing wave results: coherent positions of 1.09+-0.02 and 1.10+-0.02, coherent fractions of 0.75+-0.10 and 0.74+-0.11, respectively. However, PL reveals the higher temperature sample to be of far superior quality, due to excessive carbon incorporation at 400 deg C.