Effects of Shell Strain on Valence Band Structure and Transport Properties of Ge/Si1-xGex Core-Shell Nanowire

Various Si1-xGex shell strains induced by changing the thickness or tuning the Ge and Si contents as well as by modulating the valence band structure and hole transport characteristics of core/shell nanowire field effect transistors (FETs) have been calculated. As Si1-xGex shell thickness increases, the strained valence subbands shift upwards and warp markedly. Most of the corresponding hole effective masses of the top five subbands decrease. Meanwhile, the hole mobility of the Ge(110) nanowire increases with increasing shell thickness. As the Ge concentration in the Si1-xGex shell decreases, the strained valence subbands and hole mobility show similar shifts. As a result, our calculation indicates the possibility of improving the nanowire performance of heterostructure nanowire FETs. (C) 2010 The Japan Society of Applied Physics