THERMAL-STABILITY OF LOW-TEMPERATURE-GROWN GAAS

The thermal stability of GaAs layers grown at low temperature by molec ular beam epitaxy and subsequently annealed from 250 to 850 degrees ha s been investigated by transmission electron microscopy and Hall measu rements. The results show that the formation of arsenic precipitates i n annealed GaAs epilayers grown at low temperature and their crystallo graphical configuration are highly dependent on the temperature and du ration of the annealing. Thermal annealing at 850 degrees for 30 min c auses arsenic precipitates to become amorphous and some fraction of th e arsenic precipitates to redissolve in the crystal matrix. An analysi s of the dependence of resistivity on anneal temperature by Hall measu rements gives an activation energy of about 1.6 eV for the formation o f arsenic precipitates. Our results are discussed taking regard of the role electrically active paint defects during the precipitating proce ss.