Characterization of heavily carbon-doped InGaAsP layers grown by chemical beam epitaxy using tetrabromide

Abstract

Carbon doping in InGaAsP films using tetrabromide (CBr4) in chemical beam epitaxy has been studied, focusing on the relationship between the composition and the carrier concentration. The films with an equivalent wavelength of more than 1.4 μm have p-type conduction while the films with less than 1.3 μm have n-type conduction. Specifically, the hole concentration decreases from 7×1019 to 7×1018 cm−3 with decreasing wavelength in the 1.4–1.66 μm range, while electron concentration increases from 5×1018 to 2×1019 cm−3 with decreasing wavelength in the 1.1–1.3 μm range. Secondary-ion mass spectroscopy reveals that the incorporated carbon atom concentration is the same between an InGaAs film and a 1.4 μm equivalent wavelength InGaAsP film under a fixed CBr4 flux. Increase in gallium mole fraction monotonously increases hole concentrations under a fixed group-V mole fraction. We have found that the In1−xGaxAs1−yPy conduction type is mainly determined by two parameters: the Ga and P mole fractions, i.e., p type if x>y.