Very High Silicon Concentration by MOVPE in GaAs

Abstract

Epitaxial silicon-doped GaAs layers are grown by atmospheric pressure metalorganic vapour phase epitaxy (AP-MOVPE) using silane (SiH4) 500 ppm diluted in H2 as a dopant source gas. The grown layers are characterised by the van der Pauw method, secondary ion mass spectroscopy, room and low temperature photoluminescence experiments. The carrier concentration has a growth temperature dependence when the SiH4 partial pressure is lower than 6.7 × 10—2 Pa. However, it has no temperature dependence for SiH4 partial pressure higher than 6.7 × 10—2 Pa and the activation energy of Si incorporation varies from 0 to 2.2 eV. The carrier concentration of Si-doped GaAs is usually saturated at 6 × 1018 cm—3 level. However, in this study a carrier concentration of up to 1 × 1019 cm—3 was obtained, which in our knowledge is the highest carrier concentration ever reported for Si-doped GaAs by AP-MOVPE. Compensation ratios are firstly calculated from theoretical Hall mobility. Using room temperature photoluminescence data, theoretical fits of the photoluminescence peaks, these compensation ratios are also determined and they are compared with values obtained from mobility data.