INDIUM DOPING OF CDTE AND CD1-XZNXTE BY MOLECULAR-BEAM EPITAXY - UNIFORMLY AND PLANAR-DOPED LAYERS, QUANTUM-WELLS, AND SUPERLATTICES

CdTe and Cd1-xZnxTe layers and microstructures were doped with indium donors during their growth at low temperatures (200-220-degrees-C) by molecular-beam epitaxy under Cd overpressure. Uniform and planar doping of layers and local doping of quantum wells and superlattices are presented. Characterization techniques include secondary-ion mass spectroscopy (SIMS), capacitance-voltage and Hall-effect measurements, optical spectroscopy, x-ray double diffraction, and x-ray photoelectron spectroscopy. In the range of indium concentrations 2X10(16)-1X10(18) cm-3; the donor activation efficiency is 100% for uniform doping. A low-temperature carrier mobility of up to 5300 cm2/V s is obtained. The highest measured carrier concentration is 1.3X10(18) cm-3; at a higher doping level, strong compensation occurs, related to dopant migration and cadmium vacancy formation. Planar doping also yields almost-equal-to 100% activation efficiency for moderate values of sheet density (almost-equal-to 10(11) cm-2) but has the same limit of about 10(18) cm-3 for total carrier concentration. High-structural-quality planar-doped quantum wells and superlattices are obtained. Good localization of dopant is demonstrated by SIMS at low sheet density but at high concentration substantial migration of indium occurs.