Ultra-highly doped Si1−xGex(001):B gas-source molecular-beam epitaxy: Boron surface segregation and its effect on film growth kinetics

• DOI: 10.1063/1.1330244
• Publication Date: 2002-07-26T14:13:37Z
• Authors: H. Kim; G. Glass; P. Desjardins; J. E. Greene
• Keywords: 02 engineering and technology; 0210 nano-technology

Si 1−x Ge x (001) layers doped with B concentrations CB between 2×1016 and 2×1021 cm−3 were grown on Si(001)2×1 at Ts=500–700 °C by gas-source molecular-beam epitaxy (GS-MBE) from Si2H6, Ge2H6, B2H6. Secondary-ion mass spectrometry measurements of modulation-doped structures demonstrate that doping has no effect the incorporation probability. Steady-state surface coverages (θB θGe) determined as a function using in situ isotopically tagged temperature-programmed desorption. Results for Si0.82Ge0.18 Ts=500 show θGe remains constant 0.63 ML while bulk concentration increases linearly up to 4.6×1020 cm−3, corresponding saturation coverage θB,sat=0.5 ML, incident precursor flux ratio ξ=JB2H6/(JSi2H6+JGe2H6). is incorporated into substitutional electrically active sites over this entire range. At higher concentrations, faster than ξ there large decrease activated fraction B. The segregation enthalpy during Si0.82Ge0.18(001) growth −0.42 eV, compared −0.53 −0.64 eV Si(001):B Ge(001):B GS-MBE, respectively. Measured ratios rB=θB/xB, where xB fraction, range 15 500 temperature dependence which consistent equilibrium segregation. Film deposition rates RSiGe(CB) factor 2 increasing CB⩾5×1019 due primarily B-segregation-induced dangling bond density. above results used develop robust model predicting steady-state H θH, θB, θGe, RSiGe Ts.