Transport properties of GaAs layers grown by molecular beam epitaxy at low temperature and the effects of annealing

Abstract

The effects of growth temperature and subsequent annealing temperatures on the electrical properties of the low temperature (LT) grown GaAs have been investigated. It was found that the resistivity of the as-grown LT-GaAs layer increased with increasing growth temperature, but was accompanied by a reduction of breakdown voltage over the same temperature range. Thermal annealing of the samples caused the resistivity to rise exponentially with increasing annealing temperature TA, giving an activation energy of EA=2.1 eV. The transport of the LT-GaAs layers grown at Tg≤250 °C was found to be dominated by hopping conduction in the entire measurement temperature range (100–300 K), but following annealing at TA≳500 °C, the resistivity-temperature dependence gave an activation energy of ∼0.7 eV. The breakdown voltage VBD, for as-grown LT-GaAs was enhanced on lowering the measurement temperature, but conversely, decreased over the same temperature range following annealing at TA≳500 °C. The hopping conduction between arsenic defects, or arsenic clusters in annealed samples, is believed to be responsible for the observed electrical breakdown properties. Since the resistivities of the as-grown LT-GaAs layers are dependent, solely, on the excess arsenic, which in turn depends on the growth temperature, then the resistivities obtained can be used as a measure of the growth temperature.