Deep levels of copper-hydrogen complexes in silicon

Abstract

Complexes of substitutional copper (Cu${}_{s}$) with hydrogen in silicon are investigated by standard deep-level transient spectroscopy (DLTS) and high-resolution Laplace-transform DLTS. Hydrogen is introduced into the near-surface layer of copper-doped crystals during wet chemical etching and moved deeper into the sample by annealing Schottky contacts under reverse bias at 350--380 K. Two novel centers are observed to form in the hydrogenated region. Each of them possesses two deep levels which are only slightly different from the Cu${}_{s}$ levels. Analysis of the depth profiles allows us to identify the observed centers as complexes of Cu${}_{s}$ with one and two hydrogen atoms and reveals the formation of an electrically inactive complex with three hydrogen atoms. The identification is confirmed by the numerical modeling of the copper-hydrogen interaction which enables a quantitative description of the experimentally measured concentrations of different complexes. The variations of the Cu${}_{s}$ donor and acceptor levels due to successive hydrogenation are found to be similar to those for isoelectronic Ag and Au impurities.