TRANSPORT-PROPERTIES OF GAAS-LAYERS GROWN BY MOLECULAR-BEAM EPITAXY AT LOW-TEMPERATURE AND THE EFFECTS OF ANNEALING

The effects of growth temperature and subsequent annealing temperature s on the electrical properties of the low temperature (LT) grown GaAs have been investigated. It was found that the resistivity of the as-gr own LT-GaAs layer increased with increasing growth temperature, but wa s accompanied by a reduction of breakdown voltage over the same temper ature range. Thermal annealing of the samples caused the resistivity t o rise exponentially with increasing annealing temperature T-A, giving an activation energy of E(A)=2.1 eV. The transport of the LT-GaAs lay ers grown at T-g less than or equal to 250 degrees C was found to be d ominated by hopping conduction in the entire measurement temperature r ange (100-300 K), but following annealing at T-A>500 degrees C, the re sistivity-temperature dependence gave an activation energy of similar to 0.7 eV. The breakdown voltage V-BD, for as-grown LT-GaAs was enhanc ed on lowering the measurement temperature, but conversely, decreased over the same temperature range following annealing at T-A>500 degrees C. The hopping conduction between arsenic defects, or arsenic cluster s in annealed samples, is believed to be responsible for the observed electrical breakdown properties. Since the resistivities of the as-gro wn LT-GaAs layers are dependent, solely, on the excess arsenic, which in turn depends on the growth temperature, then the resistivities obta ined can be used as a measure of the growth temperature. (C) 1996 Amer ican Institute of Physics.