SIMS and X‐ray diffraction characterization of carbon‐doped GaAs, AlxGa1 − xAs films grown by MBE

Abstract

AbstractIn this article we report on analyses of GaAs and AlxGa1 − xAs carbon‐doped films, grown by solid source molecular beam epitaxy by using secondary ion mass spectrometry, x‐ray diffraction, and Hall effect measurement.Carbon is an amphoteric dopant, i.e. it behaves as an acceptor or a donor impurity when it occupies an As or a Ga site, respectively. Comparison between x‐ray diffraction and Hall effect measurements indicates that, for concentrations below 4 × 1019 cm−3, carbon is preferentially incorporated on As site, both in GaAs and AlxGa1 − xAs layers. We find that the presence of Al strongly enhances the substitutional carbon incorporation. SIMS analyses show that the total amount of carbon largely exceeds the substitutional carbon content recorded by HRDXD. The results can be explained considering that carbon is on substitutional as well as interstitial sites. Furthermore, we show that the interstitial carbon concentration can be reduced for both GaAs:C and AlxGa1 − xAs:C growing at an increased As4 flux and higher substrate temperature.