Impact of growth temperature and substrate orientation on dilute-nitride-antimonide materials grown by MOVPE for multi-junction solar cell application

Abstract

Nitrogen incorporation in bulk films of GaAsN, InGaAsN, and GaAsSbN films grown by metalorganic vapor phase epitaxy (MOVPE) on (100) and (311)B GaAs substrates was investigated. These films, nominally lattice-matched to a GaAs substrate, were deposited at relatively higher growth temperature (600°C) than typically used for MOVPE-grown dilute-nitride materials (~500–530°C), in order to reduce the background carbon impurity concentration. Even at these higher growth temperatures, sufficient N incorporation is achieved for targeting Eg~1eV InGaAsN and GaAsN with low background carrier concentration (1–2×1017cm−3). The presence of Sb is found to significantly inhibit N incorporation, making it challenging to achieve films of GaAsSbN grown at 600°C with a sufficient N concentration to achieve a 1eV band gap energy. For GaAsN and InGaAsN on (311)B GaAs substrates, increased N incorporation with lower background carbon concentration is observed, relative to films on (100) GaAs. By contrast, GaAsSbN on (311)B GaAs substrate exhibit lower-N incorporation relative to films on (100) GaAs, presumably due to surface site competition between Sb and N. The background hole carrier concentrations of thermally annealed InGaAsN and GaAsSbN on (311)B are about a factor of two lower than those on (100) GaAs substrate.