AsGa antisite defects formed during plastic deformation of GaAs are identified by electron paramagnetic resonance (EPR) measurements. From photo-EPR results it can be concluded that the two levels of this double donor are located near Ec −0.75 eV and Ev +0.5 eV. These values are coincident with the Fermi level pinning energies at Schottky barriers. The upper level can be related to the ’’main electron trap’’ EL2 in GaAs. Photoluminescence experiments before and after thermal annealing suggest that AsGa defects reduce the near band edge luminescence efficiency. A dislocation climb model is presented which is able to explain AsGa formation during dislocation movement. The production of AsGa antisites during dislocation motion under injection conditions in light emitting devices may thus be connected with degradation of the light output.
A method based on time-dependent measurement of charge transients has been developed to evaluate the specific resistivity of semi-insulating wafers quickly, non-destructively and with good lateral resolution. The material is inserted between capacitive electrodes. T h e time-dependent charge distribution after application of a voltage step allows evaluation of the resistivity with high accuracy in the range 1OB-lOBRcm. The technique has been elaborated to allow rapid contactless scanning of wafers for routine measurement of the lateral variation of resistivity with a resolution of about 2 mm'. The results are in agreement with conventional Hall measurements. The mechanical and electronic systems are described in detail. Scans across wafers cut from as-grown as well as annealed ingots are presented.
Magneto-optical properties of nanocomposite films obtained by partial reduction of (Ni,Mg)O and (Co,Mg)O solid solutions Cathodoluminescence and transmission electron microscopy studies in thermochemically reduced MgO:Ni crystals
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