Quasi-Ballistic $\Gamma $ - and L-Valleys Transport in Ultrathin Body Strained (111) GaAs nMOSFETs

We carefully scrutinize the potential of ultrathin body strained (111) GaAs MOSFETs to achieve better performance than other GaAs-based channel FETs at scaled channel length and with relaxed thickness requirements, thanks to L-valleys enhanced density-of-states (DoS) and carrier transport. Calibrated multi-subband Monte Carlo simulations including scattering provide the modeling framework necessary for accurate simulations. The results show that L-valley-enhanced transport most likely will not yield the ${I}_{\rm{\scriptscriptstyle ON}}$ and switching time improvements observed in simple ballistic simulations, even if considering the ideal material properties and purely phonon scattering limited transport. In fact, the increased DoS and inversion charge at the virtual source provided by the L-valleys in the strained material is counterbalanced by an increased phonon scattering rate and reduced carrier velocity.