Zeeman Spectroscopy of AN Axial Double Acceptor Bound Exciton in Molecular Beam Epitaxial Gallium Arsenide

Molecular beam epitaxy is one of the primary techniques used for the growth of state-of-the-art gallium arsenide epilayers. The sharpness of the shallow donor and acceptor bound exciton recombination photoluminescence lines in such samples is indicative of low impurity content and good morphology. However, a number of extra photoluminescence lines are frequently observed in samples grown by this technique. These lines have been associated with defects induced by growth conditions. In this work, we have investigated the photoluminescence signature of such a growth induced defect, the Y defect. A Fourier transform interferometer was used for polarization, resonant and Zeeman spectroscopy, while time-resolved photoluminescence was performed with the aid of a conventional dispersive spectrometer. The interferometric apparatus offered the necessary resolution and signal throughput capabilities for the detailed measurements reported here. The Y defect is demonstrated to be an axial double acceptor aligned along the (110) direction in the GaAs lattice, perpendicular to the (001) growth direction. Selective excitation photoluminescence spectra reveal two-hole replicas consistent with the presence of 2 holes in the bare neutral acceptor complex. From the two-hole spectrum, the ionization energy from the neutral to the singly ionized state is determined to be almost equal to the effective mass value for single acceptors.