Intrinsic carrier concentration as a function of stress in (001), (101) and (111) biaxially-Strained-Si and Strained-Si_1-xGe _x

Abstract

Intrinsic carrier concentration (n _i) is one of the most important physical parameters for understanding the physics of strained Si and Si_1-xGe _x materials as well as for evaluating the electrical properties of Si-based strained devices. Up to now, the report on quantitative results of intrinsic carrier concentration in strained Si and Si_1-xGe _x materials has been still lacking. In this paper, by analyzing the band structure of strained Si and Si_1-xGe _x materials, both the effective densities of the state near the top of valence band and the bottom of conduction band (N _c and N _v) at 218, 330 and 393 K and the intrinsic carrier concentration related to Ge fraction (x) at 300 K were systematically studied within the framework of KP theory and semiconductor physics. It is found that the intrinsic carrier concentration in strained Si (001) and Si_1-xGe _x (001) and (101) materials at 300 K increases significantly with increasing Ge fraction (x), which provides valuable references to understand the Si-based strained device physics and design.

Keywords

strain / intrinsic carrier concentration / KP theory / density of state

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