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(a) C-strained SiGe NW FET shows higher ID and steeper subthreshold slope comparing to unstrained device. (b) Unstrained SiGe NW FET suffers from punsh through in short channel. All device were measured at linear regime (Vd = 10 mV) (Inset (a) cross-section of core shell SiGe NW. (b) NWs are stacked on SOI wafer.)
(a)–(d) Effective mobility increases as temperature increases in all channel length c-strained SiGe NW FETs and long channel unstrained NW. (f) Short channel unstraine NW shows completely opposite behavior observed in Coulomb scattering dominant transport. (e) At 100 nm channel length, trends are mixed.
Low field mobility as a function of temperature shows that all c-strained SiGe NW FETs follow the phonon scattering (a)–(c). Coulomb scattering is dominant in short channel unstrained NW (f) whereas Coulomb scattering is negligible at 600 nm channel length unstrained NW (d). (e) According to Matthiessen's rule, phonon and coulomb scattering limited mobility behavior is mixed at 100 nm channel length unstrained SiGe NW. (Red dots: mobility limited by Coulomb scattering. Black dots: mobility limited by phonon scattering.)
Impurity scattering contribution is generally lower at c-strained devices comparing to unstrained devices. Transport of 40 nm channel length unstrained SiGe NW is almost fully limited by impurity scattering at all temperature range.
Summary of the parameters extracted from Eq. (7). α, β, and γ are the coefficients of Coulomb, phonon, and neutral scattering limited mobility, respectively.
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