Effect of Low Temperature on the Electron Mobility Enhancement of Strained-Si Nanowire Transistors

Abstract

Recently, interest in electronic devices operating at low temperatures has considerably increased [1]. As the nanowire/nanosheet transistors are expected as next-generation devices, it is necessary to investigate the device performance at low temperatures. In this work, we have calculated the electron channel mobility of 10x5 nm2 rectangular nanowire transistors with a [110] channel direction by using a TCAD simulator [2]. In order to investigate the effect of temperature on the electron mobility of strained channel, the two-band k·p Hamiltonian model is employed. Fig. 1(a) and Fig. 1(b) show the lowest subband structures of the unprimed and primed valleys at 300 K and 77K, respectively. The energy difference between the unprimed and primed valleys is increased as the applied stress increases. Due to the reduction of intervalley phonon scatterings and the electron repopulation, the mobility enhancement is affected. Fig. 2 shows that the population of electrons in unprimed valleys is increased as a function of tensile stress. Fig. 3(a) and Fig. 3(b) show the electron mobility and mobility enhancement at 300 K and 77 K, respectively. At 77 K, because most of electrons are resided in the unprimed valleys, the intervalley phonon scatterings are rarely occurred in the case of relaxed channel.