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Enhanced p-Type Doping in Polycrystalline CdTe Films: Deposition and Activation

2019; Institute of Electrical and Electronics Engineers; Volume: 9; Issue: 3 Linguagem: Inglês

10.1109/jphotov.2019.2902356

2156-3381

Brian E. McCandless, Wyatt K. Metzger, W.A. Buchanan, Gowri Sriramagiri, Christopher P. Thompson, Joel N. Duenow, David Albin, Søren A. Jensen, J. T. Moseley, M. M. Al‐Jassim,

Advanced Semiconductor Detectors and Materials

An in situ nonequilibrium method to increase hole density in polycrystalline CdTe thin films to 10 16 cm -3 using group V substitution on Te is presented. Single-phase CdTe films doped with P, As, and Sb were deposited at 550 °C at 100-200 nm/s onto moving cadmium sulfide/high resistance transparent buffer layer/transparent conductive oxide /glass superstrates by vapor transport deposition in Cd overpressure from high purity compound sources. Doping levels before and after activation were determined by capacitance-voltage analysis of diagnostic devices. Secondary ion mass spectrometry depth profiling confirmed dopant incorporation levels of 10 17 -10 18 atoms/cm 3 in as-deposited films. Electronic activation was carried out by post-deposition annealing in Cd or CdCl 2 vapor with fast cooling, increasing acceptor concentrations to >10 15 cm -3 for P and >10 16 cm -3 for As and Sb, compared with mid -10 14 cm -3 acceptor levels for undoped CdTe films. The activation methods are compatible with post-deposition processing presently used for high-efficiency CdTe solar cells. For the dopants As and Sb, the acceptor concentration increased by substitutional AsTe and SbTe formation, respectively, which was validated by cathodoluminescence spectroscopy.