Thermal expansion of GaAs:Te and AlGaAs:Te at low temperatures

Abstract

We studied the influence of free electrons on the lattice parameters, thermal expansion, and negative thermal expansion of GaAs:Te and AlGaAs:Te. The samples were examined at temperatures in the range of 10–295 K. Dylatometry and high-resolution x-ray diffraction were used as experimental techniques. Additionally, for the doped layer of Al0.32Ga0.68As, the free-electron concentration was changed in situ by illumination and emptying the metastable DX centers. These results were compared with those for GaAs bulk crystals examined using dylatometry. It was confirmed that n-type doping increases thermal expansion at temperatures higher than about 120 K. At lower temperatures, a phenomenon of the negative thermal expansion becomes much more pronounced for the doped GaAs sample.