Detection of a Molybdenum Acceptor Level in N-Type Silicon

Abstract

The detection of Mo in n-type Si has been reported in only a few references. An unidentified peak was detected in an n-type epitaxial layer by DLTS with an activation energy and capture cross-section of 0.255 eV and 3.5 × 10−16 cm2, respectively. These results were consistent with measurements of n-type silicon implanted with Mo. A p-type epitaxial wafer was exposed to the same epitaxial growth environment resulting in the detection of the Mo-d level, thus confirming the Mo contamination. The change in the enthalpy of the capture of electrons into the unidentified level was 14 meV resulting in the majority carrier capture cross-section being determined to be 1.2 × 10−16 cm2 assuming a multi-phonon process. Using the activation energy and enthalpy change of capture cross-section data, the change in Gibbs free energy as a function of temperature was calculated to be Ec-0.269 eV. Poole-Frenkel effect measurements determined the deep level to be an acceptor-like state. The total change in entropy was determined to be 1k, the first reported total entropy change for an acceptor level of a 4d transition metal. The measured enthalpy energy was in reasonable agreement with the reported theoretical calculation of a substitution Mo-a deep level.