Fully relaxed, strain-tuning Si1−xGex buffers were grown at very high temperatures of 950–1080C by reduced-pressure chemical vapour deposition as platforms for high quality strained Si layers. It was critical that these buffers have a low threading dislocation density to maximize carrier mobility and minimize leakage currents in high performance electronic devices. The influence of the Si1−xGex growth rate on threading dislocation density was investigated for buffers with Ge content x ≤ 0.5. In contrast to the established understanding, the threading dislocation density, in this growth regime, exhibits almost no dependence upon the Si1−xGex growth rate. It was suggested that, at these high temperatures, the gliding arms associated with dislocations had a sufficiently high velocity for the layers to relax even at the highest growth rates. Hence, no benefit was gained from reducing the growth rate, as required at lower growth temperatures to allow the threading arms to glide. The relaxed buffers produced at these high growth rates nevertheless had state-of-the-art threading dislocation density values of ~6 x 104 and ~1 x 105/cm2 for Si0.8Ge0.2 and Si0.5Ge0.5 buffers, respectively.

Effect of Growth Rate on the Threading Dislocation Density in Relaxed SiGe Buffers Grown by Reduced Pressure Chemical Vapour Deposition at High Temperature. A.Dobbie, M.Myronov, X.C.Liu, V.H.Nguyen, E.H.C.Parker, D.R.Leadley: Semiconductor Science and Technology, 2010, 25[8], 085007