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 cm 2 , 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 cm 2 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 E c -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.

Electrical Levels and Diffusion Barriers of Early 3d and 4d Transition Metals in Silicon

“…Our view is that these levels arise from defect complexes of Mo (with Si vacancies or other species) and not from single interstitial Mo. Finally, Cox [40] reported an acceptor-like level at E C − 0.269 eV (denoted as B in Fig. 1) which was ascribed to substitutional Mo.…”

Recombination via transition metals in solar silicon: The significance of hydrogen–metal reactions and lattice sites of metal atoms

“…However, the unidentified DLTS signals related to Mo in the upper half of the gap, which were observed in Refs. , could be related to Mo‐H complexes.…”

“…The majority of electrically active Mo in silicon is found at an interstitial site and is known to introduce one deep donor level in the silicon band gap close to E v + 0.30 eV . Some evidence has been presented of Mo‐related levels in the upper half of the gap . However, the most recent study of these levels suggests that these are not likely to be due to the Mo interstitial.…”

“…Some evidence has been presented of Mo‐related levels in the upper half of the gap . However, the most recent study of these levels suggests that these are not likely to be due to the Mo interstitial. In previous DLTS studies of Mo in p‐type material, as well as in our work to date, no evidence of Mo‐H complexes has been observed.…”