Analysis of Etched CdZnTe Substrates

Abstract

State-of-the-art as-received (112)B CdZnTe substrates have been examined for surface impurity contamination and polishing residue. Two 4 cm × 4 cm and one 6 cm × 6 cm (112)B state-of-the-art as-received CdZnTe wafers were analyzed. A maximum surface impurity concentration of Al = 1.7 × 10¹⁵ atoms cm⁻², Si = 3.7 × 10¹³ atoms cm⁻², Cl = 3.12 × 10¹⁵ atoms cm⁻², S = 1.7 × 10¹⁴ atoms cm⁻², P = 1.1 × 10¹⁴ atoms cm⁻², Fe = 1.0 × 10¹³ atoms cm⁻², Br = 1.2 × 10¹⁴ atoms cm⁻², and Cu = 4 × 10¹² atoms cm⁻² was observed on the as-received CdZnTe wafers. CdZnTe particulates and residual SiO₂ polishing grit were observed on the surface of the as-received (112)B CdZnTe substrates. The polishing grit/CdZnTe particulate density on CdZnTe wafers was observed to vary across a 6 cm × 6 cm wafer from ∼4 × 10⁷ cm⁻² to 2.5 × 10⁸ cm⁻². The surface impurity and damage layer of the (112)B CdZnTe wafers dictate that a molecular beam epitaxy (MBE) preparation etch is required. The contamination for one 4 cm × 4 cm and one 6 cm × 6 cm CdZnTe wafer after a standard MBE Br:methanol preparation etch procedure was also analyzed. A maximum surface impurity concentration of Al =  2.4 × 10¹⁵ atoms cm⁻², Si = 4.0 × 10¹³ atoms cm⁻², Cl = 7.5 × 10¹³ atoms cm⁻², S = 4.4 × 10¹³ atoms cm⁻², P = 9.8 × 10¹³ atoms cm⁻², Fe = 1.0 × 10¹³ atoms cm⁻², Br = 2.9 × 10¹⁴ atoms cm⁻², and Cu = 5.2 × 10¹² atoms cm⁻² was observed on the MBE preparation-etched CdZnTe wafers. The MBE preparation-etched surface contamination consists of Cd(Zn)Te particles/flakes. No residual SiO₂ polishing grit was observed on the (112)B surface.