THERMAL-STABILITY OF LOW-TEMPERATURE-GROWN GAAS

The thermal stability of GaAs layers grown at low temperature by molecular beam epitaxy and subsequently annealed from 250 to 850 degrees has been investigated by transmission electron microscopy and Hall measurements. The results show that the formation of arsenic precipitates in annealed GaAs epilayers grown at low temperature and their crystallographical configuration are highly dependent on the temperature and duration of the annealing. Thermal annealing at 850 degrees for 30 min causes arsenic precipitates to become amorphous and some fraction of the arsenic precipitates to redissolve in the crystal matrix. An analysis of the dependence of resistivity on anneal temperature by Hall measurements gives an activation energy of about 1.6 eV for the formation of arsenic precipitates. Our results are discussed taking regard of the role electrically active paint defects during the precipitating process.