Hydrogen desorption kinetics and Ge 2H 6 reactive sticking probabilities on Ge-adsorbed Si( [formula omitted

Abstract

Modeling of Si 1− x Ge x (0 1 1) gas-source epitaxy from hydride precursors requires knowledge of reactive sticking probabilities and hydrogen desorption kinetics. We use D 2 temperature programmed desorption (TPD), reflection high energy electron diffraction (RHEED), Auger electron spectroscopy (AES), and kinetic modeling to determine hydrogen desorption kinetics from, and Ge 2H 6 reactive sticking probabilities at, Si and Ge sites on Ge-adsorbed Si(0 1 1) samples with Ge surface coverages θ Ge between 0 and 1 ML. Following Ge adsorption, the samples were exposed to atomic D until saturation coverage at 250 °C. TPD spectra consist of five second-order peaks due to D 2 desorption from, in order of decreasing temperature, Si rest-atom and adatom monodeuterides, Si dideuteride, and Ge rest-atom and adatom monodeuteride phases. The maximum temperatures of all five peaks shift to lower values with increasing θ Ge. We attribute this, as in the case of Ge-adsorbed Si(0 0 1), to a decrease in Si–D and Ge–D binding energies due to long-range electronic interactions. Ge/Si(0 1 1) surface reconstructions, determined by RHEED, are “16×2” with θ Ge<0.4 ML and “2×8” at higher coverages. Quantitative θ Ge values were obtained by fitting the D 2 TPD spectra and validated using in situ AES. Based upon θ Ge vs Ge 2H 6 exposure data and modeling of the adsorption kinetics, we obtain zero-coverage Ge 2H 6 reactive sticking probabilities of 1.9×10 −2 and 4.8×10 −3 at Si and Ge sites, respectively.