AbstractCdTe etching was investigated using variable angle spectroscopic ellipsometry and glancing angle x-ray diffraction. Treatment with HNO₃:H₃PO₄ (NP) based etches was shown to form amorphous-Te surface films which spontaneously crystallize following etching. Br₂/methanol (BM) etching forms very thin amorphous-Te films. NP-etched surfaces are stable in ambient air for ∼1 hr before beginning to oxidize, while BM etched films oxidize immediately following treatment. CdTe grain boundary etching by NP was minimized using more acidic etches. Device analysis suggests that a higher Te content produces more stable back contacts by attenuating Cu diffusion. Mechanistic details of NP etching are discussed.