The electrical activity of nitrogen as an acceptor in ZnO has been investigated in two ways. First, nitrogen was introduced by means of diallylamine during metalorganic vapor phase epitaxy (MOVPE) yielding incorporation of nitrogen in the range 1016–1021 cm−3. This led to significant compensation of the natural donors with a minimum electron concentration of 5×1014 cm−3. Second, diffusion of nitrogen was carried out on undoped MOVPE layers under high pressure conditions stemming from the decomposition of NH4NO3. Conversion to p-type conductivity was observed in a systematic way with measured hole concentrations up to 6.5×1017 cm−3.
The reactivation kinetics of the acceptor behavior of carbon in GaAs layers has been studied. The reactivation was achieved by ex situ rapid thermal annealing. To follow the carbon reactivation process, a multistage annealing experiment was performed, with changes in the sample carrier concentration monitored at each stage. An analysis of these data indicates that carbon reactivation follows a first-order kinetics process that can be explained by a model which includes the effects of dopant repassivation by hydrogen retrapping during hydrogen out-diffusion, and a dependence of the attempt frequency with the carbon concentration. The reactivation occurs with an activation energy of 1.41 eV.
Carbon doping efficiency in GaAs grown by metalorganic chemical vapor deposition using intrinsic and extrinsic doping sources is studied. Independent of the carbon source, carbon hydrogen complexes are systematically present and depending on the growth conditions, carbon dimers can be present and form complexes with hydrogen as well. Carbon–hydrogen related complexes and dimers reduce the hole concentration decreasing the doping efficiency. Additionally, the carbon dimer introduces a deep level, decreases the hole mobility and hydrogen bonds stronger to it than to isolated carbon. Depending on the growth conditions it is possible to reach 100% doping efficiency with high hole mobility.
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