Free-to-bound transitions in Si-doped epitaxial Ga1−xAlxAs

Abstract
We have studied silicon‐doped Ga1−xAlxAs by low‐temperature photoluminescence as a function of aluminum composition up to x ∼0.4 and as a function of Si doping at x ∼ 0.4. We have identified a donor‐to‐acceptor pair recombination band due to Si in the spectra at 5.5 K. The Si acceptor energy is determined from the peak position of the corresponding free‐to‐bound transition, which is observed in the 75‐K continuous wave spectra or in the 5.5‐K time‐resolved spectra. It is found to vary from 35 to 62 meV in the range x ∼ 0 to 0.4 and the acceptor is suggested to be Si occuping arsenic sites. The variation of the ionization energy of SiAs with x is intermediate between that of GeAs which shows strong deviation from the effective mass theory and CAs which shows very little deviation.