As-Received CdZnTe Substrate Contamination

State-of-the-art as-received (112)B CdZnTe substrates were examined for surface impurity contamination, polishing damage, and tellurium precipitates/inclusions. A maximum surface impurity concentration of Al = 7.5 × 10 14 , Si = 3.7 × 10 13 , Cl = 3.12 × 10 15 , S = 1.7 × 10 14 , P = 7.1 × 10 13 , Fe = 1.0 × 10 13 , Br = 1.9 × 10 12 , and Cu = 4 × 10 12 atoms cm −2 was observed on an as-received 6 × 6 cm wafer. As-received CdZnTe substrates have scratches and residual polishing grit on the (112)B surface. Polishing scratches are 0.3 nm in depth and 0.1 μ m wide. The polishing grit density was observed to vary from wafer-to-wafer from ∼5 × 10 6 to 2 × 10 8 cm −2 . Te precipitate/inclusion size and density was determined by near-infrared automated microscopy. A Te precipitate/inclusion diameter histogram was obtained for the near-surface (top ~140 μ m) of a 6 × 6 cm substrate. The average areal Te precipitate/inclusion density was observed to be fairly uniform. However, there was a large density of Te precipitates/inclusions with a diameter significantly greater than the mean. Te precipitate/inclusion density >10 μ m diameter = 2.8 × 10 3 cm −3 . The large Te precipitates/inclusions are laterally non-uniformly distributed across the wafer.