The dependence of iodine incorporation in CdTe layers on the deposition conditions during metalorganic vapor phase epitaxy is investigated. The growth of the layers was carried out from dimethylcadmium and diethyltellurium in the hydrogen flow in a vertical reactor with a hot wall condition at a total pressure of 20 kPa. The total iodine concentration was determined by secondary ion mass spectrometry, the electrically active concentration was determined from the Hall effect measurement. The iodine incorporation depends on the crystallographic orientation of the substrate (were studied (100), (310), (111)A, (111)B, (211)A and (211)B), the concentration of the doping precursor (flux range 5·10–8–3·10–6 mol/min), the mole ratio of organometallic compounds (DMCd/DETe=0.25–4), growth temperature (335–390°C) and the walls of the reactor above the pedestal (hot wall zone 290–320°C). The total iodine concentration reached 5·1018 cm–3 and the activation efficiency was ~4 %. After thermal annealing in cadmium vapor at 500°C the activation efficiency was ~100 %.
The incorporation and activation of arsenic from tris(dimethylamino)arsine in CdTe layers grown by metalorganic chemical vapor deposition with dimethylcadmium and diisopropyltellurium on GaAs substrates are investigated. Arsenic incorporation into CdTe to depend on the crystallographic orientation of the layers and increases in the order (111)B<(100)<(310). Arsenic concentration in the CdTe layers is proportional to the tris(dimethylamino)arsine flow rate to the power of 1.4 and an increase with decrease of the diisopropyltellurium/dimethylcadmium ratio from 1.4 to 0.5. The as-grown CdTe:As layers had p-type conductivity with arsenic and hole concentrations of 1·1017–7·1018 and 2.7·1014–4.6·1015 cm–3, respectively, but the arsenic activation efficiency not exceeding 0.3%. After annealing in argon flow (250–450 ° C) the highest hole concentration and arsenic activation efficiency were 1·1017 cm–3 and ~4.5 % respectively. The ionization energy of arsenic determined from the temperature dependence of the hole concentration was in the range of 98–124 meV. Low-temperature photoluminescence spectra of the layers showed an emission peak with energy of 1.51 eV, which can be attributed to donor-acceptor recombination, where the acceptor is AsTe with ionization energy about 90 meV.
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