Carbon tetrabromide carbon doping of molecular beam epitaxial (GaAs) films

Abstract

GaAs films were doped with carbon up to a hole concentration of 1.3×1020 cm−3 using CBr4 vapor. The material quality of the heavily doped films was found to be better than that obtained using evaporated carbon. Improvements at the highest doping levels include better surface morphology, higher hole mobilities, significantly stronger photoluminescence, and near unity substitutional incorporation. Doping pulses created using CBr4 exhibited abrupt transitions. From the results it is suggested that the material quality of the films doped with evaporated carbon are degraded at high doping levels due to surface combination of reactive carbon species.

Effects of carbon tetrabromide flux, substrate temperature and growth rate on carbon-doped GaAs grown by molecular beam epitaxy

“…Solid source molecular beam epitaxy (SSMBE) offers the advantage of a hydrogen-free environment for growth of C-doped compound semiconductors, by eliminating the passivation of carbon acceptors by hydrogen that is commonly observed in C-doped layers grown by MOCVD or GSMBE, which use hydrides as group V sources. Hence in recent years, the usage of CBr 4 in conjunction with SSMBE systems has been increasing [6][7][8][9].…”

Surface morphology of heavily carbon-doped GaAs grown by solid source molecular beam epitaxy

“…These include unity carbon atom activation and absence of hydrogen related defects. The properties of GaAs:C grown by SSMBE, such as carrier mobility, dopant activation and lattice mismatch have been studied rather extensively [3,4], except for surface morphology for which existing reports are based mainly on GaAs:C grown by MOVPE [5,6].…”

Carbon ?-doping GaAs superlattices

“…The carbon atoms may be incorporated either from the metallorganic (MO) precursors, commonly the Ga precursor trimethylgallium (TMGa), from a separate dopant source, such as CCI4 or CBr 4, as discussed in Abernathy et al [7] or from an incandescent graphite filament. The use of CBr4 in chemical beam epitaxy (CBE) produces good quality layers with essentially all the carbon atoms incorporated as shallow acceptors and abrupt dopant profiles [8]. A complication that occurs when MO precursors are used for growth at low growth temperatures ( ~ 500 °C) is the inadvertent incorporation of hydrogen leading to the passivation of CAs acceptors by the formation of nearest-neighbour H-CAs pairs [9,10].…”

“…Corresponding values of ~ 1 nm and 2.2 x 1020 cm-3 refer to samples grown by MOVPE after annealing at 600 °C to remove grown-in hydrogen. Infrared localized vibrational mode (LVM) spectroscopy was used to determine the lattice sites occupied by the carbon atoms and to show whether or not H CAs pairs were present [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The carbon and free-carrier concentrations in the structures were determined by SIMS, ECV and Hall measurements.…”