PHOTOLUMINESCENCE INVESTIGATION OF SURFACE OXIDATION OF Cdo.gZno.,Te DETECTORS H. Chen', M. Hayes', K. Chattopadhyay', K. T. Chen%, A. Burger', J. Heffelfinger" and R. B. James** *Center for Photonic Materials and Devices, Department of Physics, Fisk University, Nashville, TN 37208. "**Advanced Electronics Manufacturing Technologies Department, Sandia National Laboratories, Livermore, CA 94550. ABSTRACT The effect of surface oxidation of Cdl.XZnTe (x = 0.1) detectors by chemical etching in hydrogen peroxide aqueous solution (H 2 0 2 ) at different concentrations and etching times was investigated by low temperature photoluminescence (PL). The treatment resulted in better surface condition evidenced by the larger 1()0, X/Idef intensity ratio and the narrower full width at half maximum of the main peak (D°, X). Peak shifts in the PL spectra associated with bound exciton lines and free to bound transition were also observed and attributed to the oxide layer. These surface effects were found to be dependent on H 2 0 2 concentration and etching time. The significance of this surface oxidation on device passivation and the subsequent improvements in the detector performance are also discussed. INTRODUCTION Over the last decade, wide bandgap semiconductor radiation detectors especially Cdl-.Zn.Te (CZT), have been known to be an attractive alternative to scintillators due to their compact size, high energy resolution and room temperature operation capability. Two typical problems associated with detector fabrication are surface conduction and injecting contacts, which greatly influence detector performance via dark current leading to a source of noise in the detector spectral response. Past efforts have been made to reduce the leakage current and consequently improve energy resolution of room temperature CZT detector via novel chemical etching. These efforts were aimed at restoring surface stoichiometry and removing damaged surface layers resulted from mechanical polishing" 2 . However, detector performance still continues to be limited by the surface component of the dark current. Recent study has indicated that this current can be further reduced by intentional surface oxidation via H 2 0 2 aqueous solution etching 3 . Although various reports in the past have been made on the oxidized CdTe and CdZnTe surfaces 4 ' 5 ' 6 , little has been published about H.0 2 chemical oxidation of CZT surfaces, especially with regard to detector performance. In this study, we investigate the effect of surface oxidation of detector grade Cd,-,ZnTe (x = 0.1 ) crystals by hydrogen peroxide solution etching at different etching times and different concentrations via low temperature photoluminescence (PL) characterization technique. PL is a very useful method of measuring surface recombination and shallow level impurities in semiconductor 65 Mat. Res. Soc. Symp. Proc. Vol. 487 ©1998 Materials Research Society