Growth of Si{sub 1{minus}x}Ge{sub x}(011) on Si(011)16{times}2 by gas-source molecular beam epitaxy: Growth kinetics, Ge incorporation, and surface phase transitions
- Materials Science Department, Coordinated Science Laboratory, and Materials Research Laboratory, University of Illinois, 1101 West Springfield Avenue, Urbana, Illinois, 61801 (United States)
Single crystal Si{sub 1{minus}x}Ge{sub x}(011) layers with x{le}0.35 have been grown on double-domain Si(011){open_quotes}16{times}2{close_quotes} surfaces from Si{sub 2}H{sub 6}/Ge{sub 2}H{sub 6} mixtures at temperatures T{sub s}=400{endash}950{degree}C. D{sub 2} temperature programmed desorption was used to show that the structure of the Si(011){open_quotes}16{times}2{close_quotes} surface unit cell, more correctly written as [{sub 2}{sup 17}{sub 2}{sup 1}] since the unit cell vectors are nonorthogonal, is composed of 16 adatoms and eight {pi}-bonded dimers with a dangling bond density half that of the 1{times}1 surface. Si{sub 1{minus}x}Ge{sub x}(011) overlayers are {open_quotes}16{times}2{close_quotes} when x{lt}x{sub c}(T{sub s}) and {open_quotes}2{times}8{close_quotes} with x{gt}x{sub c}(T{sub s}). The value of x{sub c} decreases from {approx_equal} 0.10 at T{sub s}=475{degree}C to 0.08 at 550{degree}C to 0.06 at 650{degree}C. Both the {open_quotes}2{times}8{close_quotes} and {open_quotes}16{times}2{close_quotes} Si{sub 1{minus}x}Ge{sub x}(011) surface reconstructions gradually and reversibly transform to 1{times}1 at T{sub s} between 650 and 725{degree}C. Film growth kinetics exhibit three distinct regimes. At low temperatures (T{sub s}{approx_lt}500{degree}C), the film deposition rate R{sub SiGe} decreases exponentially with 1/T{sub s} in a surface-reaction-limited growth mode for which the rate-limiting step is hydrogen desorption from Si and Ge monohydride phases. R{sub SiGe} becomes essentially constant with T{sub s} in the intermediate impingement-flux-limited range, T{sub s}=500{endash}650{degree}C. At T{sub s}{gt}650{degree}C, R{sub SiGe} increases again with T{sub s} due initially (T{sub s}{approx_equal}650{endash}725{degree}C) to an increase in the steady-state dangling bond coverage as the surface reconstruction gradually transforms to 1{times}1. The continued increase in R{sub SiGe} at even higher T{sub s} is associated with strain-induced roughening. Ge/Si ratios in as-deposited films are linearly proportional to the incident Ge{sub 2}H{sub 6}/Si{sub 2}H{sub 6} flux ratio J{sub Ge{sub 2}H{sub 6}}/J{sub Si{sub 2}H{sub 6}} and nearly independent of T{sub s} indicating that the reactive sticking probabilities of Si{sub 2}H{sub 6} and Ge{sub 2}H{sub 6} have very similar temperature dependencies. R{sub SiGe}(J{sub Ge{sub 2}H{sub 6}}/J{sub Si{sub 2}H{sub 6}},T{sub s}) in both the surface-reaction-limited and flux-limited regimes is well described by a simple kinetic model incorporating second-order dissociative chemisorption and second-order hydrogen desorption as rate-limiting steps. {copyright} {ital 1999 American Institute of Physics.}
- OSTI ID:
- 300134
- Journal Information:
- Journal of Applied Physics, Vol. 85, Issue 1; Other Information: PBD: Jan 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Kinetics of Si{sub 1{minus}x}Ge{sub x}(001) growth on Si(001)2{times}1 by gas-source molecular-beam epitaxy from Si{sub 2}H{sub 6} and Ge{sub 2}H{sub 6}
Ultra-highly doped Si{sub 1-x}Ge{sub x}(001):B gas-source molecular-beam epitaxy: Boron surface segregation and its effect on film growth kinetics