Low-Frequency Noise in Si_1-xGe_x p-Channel Metal Oxide Semiconductor Field-Effect Transistors

Abstract

Low-frequency noise (LFN) in Si 1- x Ge x p-channel Metal Oxide Semiconductor Field-Effect Transistors (pMOSFETs) with a relatively wide range of Ge fraction x =0.2, 0.5, 0.7, and Si 1- x Ge x thickness d SiGe of 2–14 nm are investigated. Although LFN of Si 1- x Ge x pMOSFETs seems to be complicated functions of d SiGe and Ge fraction, it is shown that LFN in Si 1- x Ge x pMOSFETs can be lower than that in conventional Si pMOSFETs. Moreover, in order to evaluate the trap density at the Si 1- x Ge x /Si heterostructure interface, the noise power at bias conditions showing the maximum transconductance g mMAX is examined. At the bias conditions, drain current is confirmed to flow mainly in the buried Si 1- x Ge x channel, but not in the surface Si channel. Surface generation current is also examined to evaluate the trap density at the interface between the gate oxide and the Si capping layer. The dependence of the noise power on d SiGe and Ge fraction corresponds well to that of g mMAX , but not to that of the surface generation current. It is concluded that the noise characteristics at the g mMAX bias conditions reflect the trap density at the Si 1- x Ge x /Si heterostructure interface, and correspond well to g mMAX behavior.