CVD Growth of GeSnSiC Alloys Using Disilane, Digermane, Tin Tetrachloride and Methylsilane

Abstract

In this study, Ge1-x-y-zSnxSiyCz layers (0.01≤x≤ 0.06, 0≤y≤0.02 and 0≤z≤0.01) have been successfully grown at 280-330 ¢ªC on Ge and Si by using RPCVD technique. It was demonstrated that the quality of epitaxial layers is dependent on the growth parameters, layer thickness and the quality of Ge virtual layer. It was found that a proper strain balance in the matrix during the epitaxy where the Si is adjusted carefully with the Sn flux improves the incorporation of Sn in Ge matrix. A similar improvement of Sn incorporation has been observed for phosphorous, boron and carbon doping in GeSn layers as well. This is explained by the compensation of the compressive strain caused by Sn by the tensile strain induced by Si to obtain the minimum energy in Ge matrix. This behavior was not observed for relaxed GeSn layers and Sn incorporation could be controlled only by the growth parameters. The thermal stability of GeSn is an important integration issue for device fabrication. The thermal stability of P- and B-doped GeSn layers was studied by rapid thermal annealing (RTA) in range of 400-600 ¢ªC and compared with intrinsic layers. The GeSn layers were stable up to 550 ¢ªC while the P-doped layers showed strain relaxation readily at 450 ¢ªC. The epitaxial quality of epi-layers was evaluated in terms of oxygen and water vapor contamination. The level of oxygen during epitaxy was as low as 10 ppb and the contamination amount was found as low as 1017 cm-3.