X-ray diffractometry of AlGaAs/GaAs superlattices and GaAs in the temperature range 5-295 K

The temperature dependence of the lattice constants of Al_xGa_{1 - x}As/GaAs superlattices MBE-grown on (001) oriented GaAs substrates was determined by X-ray diffractometry. The thermal expansion coefficients of these materials become negative at low temperatures, like that of GaAs and other tetrahedrally bonded covalent solids. The temperature dependence of the stress in these structures was also studied; although its value increases as temperature decreases, strain remains elastic down to 5 K.