Intrinsic carbon incorporation in very high purity MOVPE GaAs

Abstract

The limits of intrinsic carbon incorporation in very high purity GaAs grown by atmospheric pressure metalorganic vapor phase epitaxy (MOVPE) were investigated by using a MOVPE system designed specifically for high purity growth along with many sources of highly purified trimethylgallium (TMG) and arsine. We have systematically grown series of layers while varying the growth temperature, gas phase stoichiometry (V/III ratio) and growth rate. In addition we studied the effects of in situ arsine purification on impurity incorporation. Donor and acceptor densities were reliably determined from fitting the temperature dependence of the electron density and mobility. Lineshape analysis of donor to acceptor photoluminescence transitions provided the relative amounts of carbon and zinc acceptors. This work determined a baseline for the minimum carbon incorporation of N C ≥ 5 × 10 13 cm −3, and in addition, achieved a new standard for the electron mobility in n-type GaAs grown with TMG and AsH 3 with a peak mobility of μ(48 K) = 213,000 cm 2/ V⋯ s. Carbon incorporation showed a —1.3 power law dependence on the V/III ratio and was found to be controlled by processes with opposite temperature dependencies at high and low temperatures, thereby reaching a minimum around T g = 640 ± 20° C.