Precise Determination of the Direct-Indirect Band Gap Energy Crossover Composition in Al_xGa_(1-x)As

摘要

MBE grown Al_xGa_(1-x)As samples, with x in the range 0.282-0.424, were studied by using time-integrated and time-resolved photoluminescence spectroscopy, photo-modulation reflectance spectroscopy and photoluminescence excitation spectroscopy. The direct and indirect band gap transitions are observed simultaneously in two Al_xGai_(1-x)As samples with x = 0.387 and 0.396. An exact determination of the direct-indirect crossover composition at low temperatures is found at a direct band gap energy of 2.059 eV, which corresponds to a aluminum content of [Al] = 38.4 ± 0.3%.