Photoemission spectroscopy of GaAs:As photodiodes

We report on photoemission measurements of molecular-beam-epitaxy-grown GaAs p-i-n structures, in which the optically active insulating GaAs layer contains As precipitates (GaAs). GaAs is formed by low-temperature growth of GaAs at 225°C, followed by an anneal at 600°C. Layers grown in this way have been reported to be sensitive to subband-gap light. The measured barrier height of 0.7 eV, extracted from a well-behaved Fowler plot, indicates that the mechanism for photodetection involves arsenic clusters embedded in GaAs acting as internal Schottky barriers.