Behaviors of impurities in Cd 0.85Zn 0.15Te crystals grown by vertical Bridgman method

Abstract

The distribution of impurities Li, Na, Mg, Al, S, Cl, K, Cu, In, Ga and Ag in Cd 0.85Zn 0.15Te crystal ingots grown by vertical Bridgman method has been investigated using the inductively coupled plasma mass spectrometry (ICP/MS). It is found that the segregation coefficients of Al, S, In and Ga are larger than unit, which leads to their enrichment in the first-to-freeze portion of ingots, while the segregation coefficients of Li, Na, Mg, Cl, K, Cu and Ag are less than unit, which leads to their enrichment in the last-to-freeze portion of ingots. Resistivity measurements reveal that Mg, Al, S, Cl, In and Ga are positive to increase the resistivity of Cd 0.85Zn 0.15Te, while Li, Na, K, Cu, and Ag are negative. Infrared (IR) transmission measurements and Hall measurements indicate that the free carrier absorption within the both impurity enriching portions decreases IR transmission and causes a decrease in IR transmission with the decrease of wavenumber. After an annealing processing, the concentration of all the impurities is highly reduced and the crystal properties are remarkably improved.