A detailed study was made of the p-type doping of Te-based compounds during molecular beam epitaxy, using N atoms which were produced by a direct-current glow plasma source. The samples were characterized by using capacitance-voltage, Hall effect, low-temperature reflectivity and luminescence, double-crystal X-ray diffraction, nuclear reaction analysis and secondary ion mass spectroscopy. It was found that doping introduced shallow hydrogenic acceptors, NTe. In the case of ZnTe, doping to the extent of 1020/cm3 could be obtained when some 1.5 x 1020/cm3 of N atoms were incorporated into the layer. This doping level decreased considerably, in the case of CdZnTe and ZnMgTe, as the Zn content decreased. The highest concentration which was obtained for CdTe was 1018/cm3. In ZnTe, the incorporation of N atoms in the NTe configuration led to a noticeable change in the lattice parameter. No such change was observed in N-doped CdTe layers. The X-ray diffraction pattern of N-doped ZnTe on ZnTe pseudo-superlattices permitted the Zn-N bond distance to be estimated at 0.216nm. A study of the doping efficiency as a function of the growth conditions indicated that the compensation mechanism was related to the formation of N interstitial defects, or complex defects which involved metal vacancies, but no deep center was detected in the luminescence. A comparison of various doped telluride materials indicated that the presence of Zn atoms strongly enhanced the solubility limit of NTe. It was argued that the Zn-Te distance was the closest fit to the metal-N bond distance, and that this minimized the elastic contribution to the formation energy of the NTe acceptor. Thus, the doping efficiency decreased when the alloy lattice parameter increased.

T.Baron, K.Saminadayar, N.Magnea: Journal of Applied Physics, 1998, 83[3], 1354-70