Growth of Silicon(1-x) Germanium(x) from Disilane and Digermane by Gas-source Molecular Beam Epitaxy PDF Download

Author: Thomas Richard Bramblett
Publisher:
ISBN:
Category :
Languages : en
Pages :

Get Book Here

Book Description
The growth rate R of Si(001), Ge(001), and $\rm Si\sb{1-x}Ge\sb{x}(001)$ films deposited on Si(001)2 $\times$ 1 substrates from $\rm Si\sb2H\sb6$ and $\rm Ge\sb2H\sb6$ by gas-source molecular-beam epitaxy (GS-MBE) were determined as a function of temperature T$\sb{\rm s}$(300-950$\sp\circ$C) and impingement flux J (0.3-$7.7\times10\sp{16}$ cm$\sp{-2}$ s$\sp{-1}$). R(T$\sb{\rm s}$,J) curves for Si and Ge films were well described using a model, with no fitting parameters, based upon dissociative chemisorption followed by a series of surface decomposition reactions with the rate-limiting step being first-order hydrogen desorption from the surface monohydride. The hydrogen desorption activation energy for Si and Ge surfaces were found to be 2.04 eV and 1.56 eV, respectively. The zero-coverage reactive sticking probability in the impingement-flux-limited growth regime was found to be 0.036 and 0.052 for $\rm Si\sb2H\sb6$ and $\rm Ge\sb2H\sb6,$ respectively. The growth rate of SiGe alloys R$\sb{\rm SiGe}$ as a function of the bulk Ge content x was found to be a complex. In the surface-reaction-limited regime, R$\sb{\rm SiGe}$ increased with Ge surface coverage $\theta\sb{\rm Ge}$ due to the lower activation energy of H$\sb2$ desorption from Ge than from Si. However, in the impingement-flux-limited regime R$\sb{\rm SiGe}$ decreases with $\theta\sb{\rm Ge}$ due to the lower reactive sticking probability of $\rm Si\sb2H\sb6$ on Ge surface sites with respect to on Si sites. The Ge fraction, x1$\sb{\rm Ge}$, of SiGe alloys was determined as a function of growth temperature T$\sb{\rm s}$ and incident flux ratios $\rm J\sb{Ge2H6}/J\sb{Si2H6}.$ The results were explained by a kinetic model accounting for four simultaneous reaction pathways: reaction of $\rm Si\sb2H\sb6$ with Si surface sites, $\rm Si\sb2H\sb6$ with Ge sites, $\rm Ge\sb2H\sb6$ with Si sites, and $\rm Ge\sb2H\sb6$ with Ge sites. The cross-term reactive sticking probabilities, $\rm S\sbsp{Ge2H6}{Si}$ and $\rm S\sbsp{Si2H6}{Ge}$, were estimated to be 0.33 and $5.2\times10\sp{-3}$ respectively.