Interactions of hydrogen with vanadium in crystalline silicon

Abstract

In this work, we have investigated interactions of vanadium with hydrogen in n‐ and p‐type float zone grown silicon using deep level transient spectroscopy (DLTS), Laplace DLTS, capacitance‐voltage and secondary ion mass spectroscopy measurements (SIMS). Vanadium was introduced into Si wafers by ion implantation with subsequent heat treatments at 800 °C for removing the implantation induced lattice damage. In the DLTS spectra of the annealed samples, we have observed two deep level states due to interstitial vanadium (Vi) atoms in n‐type Si and one in p‐type Si. A comparison of concentration profiles of the Vi atoms with those for the total concentration of V measured by SIMS has shown that at the projected implantation depth the [Vi]/[Vtotal] ratio is less than 0.05 at chemical concentration of vanadium of 1 × 1015 cm−3, so the majority of V atoms are in electrically inactive states in this region. At lower chemical concentrations of vanadium, similar values of [Vi] and [Vtotal] are observed. After the treatment of the n‐type V‐doped samples in a remote hydrogen plasma at room temperature, we have found that the concentration of the Vi atoms decreases while additional electron traps emerge in the DLTS spectra. A trap with the highest concentration has been attributed to a vanadium–hydrogen complex. In the p‐type Si:V samples, no new levels have emerged in the DLTS spectra after the H‐plasma treatments. It is suggested that in p‐type Si:V an interaction of H atoms with the Vi atoms is suppressed because of the Coulombic repulsion of positively charged Vi and hydrogen defects. It is argued that no electrically active defects are formed in either the n‐ or p‐type Si:V samples due to possible interactions of hydrogen with electrically inactive V‐related defects. We present evidence that annealing of the n‐type Si:V samples in the temperature range 75–125 °C following the application of hydrogen plasma results in up to 20% decrease in the total concentration of electrically active V‐related defects, indicating the formation of some electrically inactive V–H complexes. Heat treatments at temperatures above 175 °C have resulted in the disappearance of all the V–H complexes and recovery of electrical activity of the Vi atoms.