Incorporation of accelerated low-energy (50–500 eV) In+ ions in Si(100) films during growth by molecular-beam epitaxy

Abstract

A single-grid broad-beam ion source was used for low-energy (50–500 eV) accelerated In+ ion beam doping during growth of Si(100) layers by molecular-beam epitaxy. Indium incorporation behavior was studied as a function of ion energy (E+In=50–500 eV), substrate temperature (Ts=500–1050 °C), ion flux (J+In=1×109–5×1012 cm−2 s−1), and Si growth rate (R=0.1–1.3 nm s−1). Dopant concentration profiles obtained using secondary ion mass spectroscopy showed that abrupt doping profiles were obtained at Ts<900 °C and R=0.7 μm h−1, the incorporation probability σ+In was close to unity for E+In≥200 eV, while σ+In was less than unity and decreased gradually with increasing Ts for E+In≤100 eV. At Ts≥900 °C, σ+In decreased rapidly with increasing Ts for all ion energies. The incorporation results are interpreted using a qualitative model based on different types of binding sites for In with incident energies ranging from thermal to 500 eV. A procedure, utilizing accelerated ions, for the growth of ultrathin doped layers is also suggested.