The microprecipitates in the as-grown undoped and In-doped semi-insulating GaAs single crystals have been ex- amined by JEM 200 CX transmission electron microscope.The microprecipitates consist of GaAs polycrystalline...The microprecipitates in the as-grown undoped and In-doped semi-insulating GaAs single crystals have been ex- amined by JEM 200 CX transmission electron microscope.The microprecipitates consist of GaAs polycrystalline grains of 5～100nm in size have been evidenced in dislocated crystals.Energy dispersive X-ray analysis shows that the mieropreeipitates are predominately arsenic-rich GaAs.The As/Ga atomic ratio of the microprecipitates in In-doped crystal is higher than that of undoped crystal.It is suggested that the formation of the microprecipitates may be induced by the local fluctuation of compositional undercooling during crystal growth.展开更多
Properties of GaAs single crystals grown at low temperatures by molecular beam epitaxy (LTMBE GaAs) have been studied. The results show that excessive arsenic atoms of about 1020 cm?3 exist in LTMBE GaAs in the form o...Properties of GaAs single crystals grown at low temperatures by molecular beam epitaxy (LTMBE GaAs) have been studied. The results show that excessive arsenic atoms of about 1020 cm?3 exist in LTMBE GaAs in the form of arsenic interstitial couples, and cause the dilation in lattice parameter of LTMBE GaAs. The arsenic interstitial couples will be decomposed, and the excessive arsenic atoms will precipitate during the annealing above 300°C. Arsenic precipitates accumulate in the junctions of epilayers with the increase in the temperature of annealing. The depletion regions caused by arsenic precipitates overlap each other in LTMBE GaAs, taking on the character of high resistivity, and the effects of backgating or sidegating are effectively restrained.展开更多
文摘The microprecipitates in the as-grown undoped and In-doped semi-insulating GaAs single crystals have been ex- amined by JEM 200 CX transmission electron microscope.The microprecipitates consist of GaAs polycrystalline grains of 5～100nm in size have been evidenced in dislocated crystals.Energy dispersive X-ray analysis shows that the mieropreeipitates are predominately arsenic-rich GaAs.The As/Ga atomic ratio of the microprecipitates in In-doped crystal is higher than that of undoped crystal.It is suggested that the formation of the microprecipitates may be induced by the local fluctuation of compositional undercooling during crystal growth.
文摘Properties of GaAs single crystals grown at low temperatures by molecular beam epitaxy (LTMBE GaAs) have been studied. The results show that excessive arsenic atoms of about 1020 cm?3 exist in LTMBE GaAs in the form of arsenic interstitial couples, and cause the dilation in lattice parameter of LTMBE GaAs. The arsenic interstitial couples will be decomposed, and the excessive arsenic atoms will precipitate during the annealing above 300°C. Arsenic precipitates accumulate in the junctions of epilayers with the increase in the temperature of annealing. The depletion regions caused by arsenic precipitates overlap each other in LTMBE GaAs, taking on the character of high resistivity, and the effects of backgating or sidegating are effectively restrained.
