Strain relaxation of graded SiGe buffers grown at very high rates

The strain relaxation in compositionally graded SiGe alloy buffers was stud ied as a function of growth temperature and growth rate. We have used a pla sma enhanced CVD technique that we call low energy plasma enhanced chemical vapour deposition (LEPECVD) to access growth rates in the range of 0.9-3.8 nm/s at substrate temperatures between 640 and 725 degrees C. The samples were analysed by X-ray reciprocal space mapping, transmission electron micr oscopy and defect etching. Despite the very high growth rate, the structura l properties of the buffers are identical to buffers grown at rates one or two orders of magnitude lower. The threading dislocation density is shown t o decrease significantly with increasing temperature in the investigated ra nge. (C) 2000 Elsevier Science S.A. All rights reserved.