The Characterization of Intentional Dopants in HgCdTe using Sims, Hall-Effect, and C-V Measurements

Abstract

ABSTRACTThe properties of selected dopants in liquid-phase epitaxial (LPE) layers of HgCdTe have been studied using secondary ion mass spectrometry (SIMS), Hall-effect, and capacitance-voltage (C-V) measurements. The layers were grown from Hg-rich melts on {111}-oriented CdTe and CdZnTe single-crystal substrates. Diodes, for the C-V measurements, were homojunctions formed by ion implantation or heterojunctions formed by the growth of a second layer on the base layer. Dopant concentration distributions in both single- and double-layer structures were characterized by SIMS and C-V measurements. The dopant profiles measured by SIMS were quantified using relative sensitivity factors calculated from ion implanted impurity profiles measured on standard reference samples. Using specialized SIMS techniques, such as molecular ion spectrometry, As concentrations as low as 2 × 1015 cm−3 have been measured. In the HgCdTe:In/HgCdTe:As system minimal dopant interdiffusion is observed in SIMS profiles. The growth of the second layer has insignificant effect on the As distribution in the base layer, and C-V data indicate that the electrical properties change only slightly. Carrier types and concentrations were determined by Hall effect and C-V measurements. Good agreement between dopant concentrations and carrier concentrations was observed, indicating 100% activation of the dopant atoms, for all dopants studied. Examples of implant calibration profiles, dopant concentration distributions, carrier concentration vs temperature measurements, and 1/C2 vs V data are presented, along with graphs and tables comparing dopant profiles with electrical properties.