Electron drift mobility model for devices based on unstrained andcoherently strained Si1-xGex grown on <001>silicon substrate |
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Authors: | Manku T. Nathan A. |
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Affiliation: | Dept. of Electr. & Comput. Eng., Waterloo Univ., Ont.; |
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Abstract: | The electron drift mobility for unstrained and coherently strained Si1-xGex grown on a <001> silicon substrate is analytically obtained for Ge fractions less than 30%. The method is based on the following two assumptions: the conduction bands of the unstrained alloy are Si-like for Ge fraction less than 30%, and in the case of the coherently strained alloy, strain-induced energy shifts occur in the conduction band valleys. The shifts in energy yield two different mobility values: one corresponding to the growth plane with a value larger than the unstrained mobility, and the other parallel to the growth direction and correspondingly smaller in value. In comparison to silicon, the results show a degradation of both the unstrained mobilities for doping levels up to 1017 cm-3. Beyond this doping level, the strained mobility component parallel to the growth direction becomes slightly larger than the mobility of silicon |
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