LAUSR

Short-channel AlGaAs/GaAs High Electron Mobility Transistors (HEMTs) with gate lengths ranging up to 10 nm were fabricated using electron-beam lithography process. Transconductance starts to rise rapidly as the gate length becomes on the order of the inelastic mean free path of electrons in case of our devices below 80 nm. After reaching a maximum at around 40 nm, it is observed that both the measured transconductance and the subsequently extracted effective electron velocity drop rapidly with further reduction in gate length. We investigated this behavior with a transient transport model based on the retarded Langevin equation (RLE), which indicates the existence of a minimum acceleration length needed for the carriers to reach the overshoot velocity. Also, it clearly shows a degradation of the overshoot. This approach confirms the overshoot is limited by having a minimum acceleration length to reach the peak value of the overshoot due to a source resistance.