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
Low temperature(77 K)photoluminescence measurements have been performed on different GaAs substrates to evaluate the GaAs crystal quality.Several defect-related luminescence peaks have been observed,including 1.452 eV...Low temperature(77 K)photoluminescence measurements have been performed on different GaAs substrates to evaluate the GaAs crystal quality.Several defect-related luminescence peaks have been observed,including 1.452 eV,1.476 eV,1.326 eV peaks deriving from 78 meV GaAs antisite defects,and 1.372 eV,1.289 eV peaks resulting from As vacancy related defects.Changes in photoluminescence emission intensity and emission energy as a function of temperature and excitation power lead to the identification of the defect states.The luminescence mechanisms of the defect states were studied by photoluminescence spectroscopy and the growth quality of GaAs crystal was evaluated.展开更多
We fabricate photonic crystal slab microcavities embedded with GaAs quantum dots by electron beam lithography and droplet epitaxy. The Purcell effect of exciton emission of the quantum dots is confirmed by the micro p...We fabricate photonic crystal slab microcavities embedded with GaAs quantum dots by electron beam lithography and droplet epitaxy. The Purcell effect of exciton emission of the quantum dots is confirmed by the micro photoluminescence measurement. The resonance wavelengths, widths, and polarization are consistent with numerical simulation results.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.
基金Project supported by the National Natural Science Foundation of China(Grant No.21972103)the National Key Research and Development Program of China(Grant No.2016YFB040183)Research and Development Program of Shanxi Province,China(Grant No.201703D111026)
文摘Low temperature(77 K)photoluminescence measurements have been performed on different GaAs substrates to evaluate the GaAs crystal quality.Several defect-related luminescence peaks have been observed,including 1.452 eV,1.476 eV,1.326 eV peaks deriving from 78 meV GaAs antisite defects,and 1.372 eV,1.289 eV peaks resulting from As vacancy related defects.Changes in photoluminescence emission intensity and emission energy as a function of temperature and excitation power lead to the identification of the defect states.The luminescence mechanisms of the defect states were studied by photoluminescence spectroscopy and the growth quality of GaAs crystal was evaluated.
基金supported by a Grant-in-Aid for Scientific Research from the Ministry of Education,Science,Sports,and Culture of Japan under Grant No.20340080.
文摘We fabricate photonic crystal slab microcavities embedded with GaAs quantum dots by electron beam lithography and droplet epitaxy. The Purcell effect of exciton emission of the quantum dots is confirmed by the micro photoluminescence measurement. The resonance wavelengths, widths, and polarization are consistent with numerical simulation results.
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.
