Metal/n-CdTe interfaces: A study of electrical contacts by deep level transient spectroscopy and ballistic electron emission microscopy

This paper summarises the characteristics of chemically etched CdTe surfaces obtained by photoluminescence studies and the results of extensive transport measurements involving metal contacts fabricated on them. Fermi level pinning at five discrete levels; 0.40 +/- 0.02, 0.65 +/- 0.02, 0.73 +/- 0.02, 0.96 +/- 0.04 and 1.18 +/- 0.02 eV has been observed. Deep level transient spectroscopy (DLTS) and ballistic electron emission microscopy (BEEM) experiments have been performed on contacts made under the same conditions to compare and confirm these results. DLTS reveal similar values for electron traps in the band gap confirming a relationship between Fermi level pinning and bulk defect levels. BEEM experiments performed on contacts showing I-V barrier heights of 0.96 eV reveal significant planar non-uniformity but confirm 0.96 eV as the controlling barrier height or charge transport across the junction. (C) 1998 Elsevier Science Ltd. All rights reserved.