Near-band-edge photoluminescence from chemically treated CdTe surfaces

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Abstract
The effects of chemical etching and aging under atmospheric conditions have been investigated in In doped, bulk CdTe using photoluminescence (PL) spectroscopy. The etchants studied included Br2/CH3OH, KOH/CH3OH, Na2S2O4 /NaOH, and K2Cr2O7 /HNO3. The results indicate a large enhancement of the 1.5896‐eV excitonic feature due to chemical treatment and aging. The 1.5896‐eV peak was previously shown to originate from a native defect involving a Cd vacancy. On this basis, we interpret the primary perturbation to be a small loss of Cd within the sampling region. Previous studies have reported substantial loss of Cd in the near‐surface region, within ∼25 A of the surface, as a result of etching in Br2/CH3OH. In contrast, a much smaller loss over a possibly larger depth is observed here. The Cd loss is, most likely, substantial nearest to the surface and extends deeper in but with less severity. The implications of these results on interpreting PL spectra, device processing, and long term stability are considered.