Incorporation and activation of arsenic in single-crystal CdTe layers grown by metalorganic chemical vapor deposition

Abstract

The electrical properties of arsenic doped CdTe epitaxial layers grown on GaAs (100) substrates by metalorganic chemical vapor deposition with dimethylcadmium and diethyltellurium are investigated. Tris(dimethylamino)arsine was used as the arsenic source. CdTe layers with arsenic concentration from 1.6·1017 cm−3 to 1.5·1018 cm−3 were obtained by varying only diethyltellurium/dimethylcadmium mole ratio from 6.2 to 0.5. The as-grown CdTe:As layers had p-type conductivity with hole concentration about 2·1015 cm−3 within diethyltellurium/dimethylcadmium mole ratio 1–6.2 and n-type at diethyltellurium/dimethylcadmium = 0.5. Post-growth annealing (250–500 °C) were used to increase the activation efficiency of arsenic. The highest hole concentration was 2.1·1017 cm−3 at arsenic concentration of 4.5·1017 cm−3, but the maximum activation efficiency approximately of 85% was achieved at lower concentration levels. The ionization energy of AsTe acceptor determined from temperature-dependent Hall measurements was in the range of 96–112 meV. Low-temperature photoluminescence emission spectra of arsenic doped CdTe layers showed a peak at ~1.51 eV which is associated with AsTe acceptor with ionization energy about 90 meV. Possible mechanisms of arsenic compensation in CdTe by intrinsic defects and the AX-centers formation are discussed.