Boron impurity anti-site defects in p-type gallium-rich gallium arsenide

It is shown that gallium arsenide crystals grown from gallium-rich melts encapsulated in boric oxide contain boron impurities, some fraction of which occupy arsenic lattice sites. In compensated material these acceptor defects are in negative charge state and give rise to infrared absorption due to localised vibrational modes (LVM) at 601 cm-1 (11BAs) and 628 cm 1(10BAs). The authors demonstrate for the first time that in p-type material neutral BAs defects are present although they give no detectable LVM absorption: their presence is revealed by tuning the position of the Fermi level, EF, to the point where it coincides with the acceptor electronic level. This is achieved by introducing deep-hole traps by electron irradiation and then fine tuning of EF is effected by varying the temperature of the sample. They estimate the BAs acceptor level to be somewhat greater than 0.2 eV above the valence band and there is a possibility that it is the previously reported level at 0.23 eV. The level at 0.077 eV is probably due to an intrinsic defect.

Source:IOPscience

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