Effect of arsenic source on the growth of high‐purity GaAs by molecular beam epitaxy

We report growth of ultrapure GaAs by molecular beam epitaxy (MBE) and show that the arsenic source has a dramatic effect on the purity. With every thing else the same, by changing the arsenic source from 6N grade double refined chunks to a 7N grade slug which closely fits the 35 cm3 crucible, the deep electron trap and the residual acceptor densities were reduced by nearly two orders of magnitude. When intentionally doped with Si to an electron density of 3×1013 cm−3, the measured mobility at 77 K was 205 600 cm2 V−1 s−1, which increased to 294 700 cm2 V−1 s−1 at 42 K. These mobilities are the highest ever observed in intentionally n‐doped MBE GaAs. Low‐temperature photoluminescence studies of both undoped and Si‐doped GaAs layers grown with the As slug show a marked decrease in acceptor‐ and defect‐related luminescence over that observed when the As chunks are used. Our study conclusively proves that the major source of residual acceptor impurities and typical MBE GaAs traps observed by deep level trans...

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