Degradation of the transconductance of a gate-modulated generation current in nMOSFET

The degradation of transconductance (G) of a gate-modulated generation current IGD in a LDD nMOSFET is investigated. The G curve shifts rightward under the single electron-injection-stress (EIS). The trapped electrons located in the gate oxide over the LDD region (QL) makes the effective drain voltage diminish. Accordingly, the G peak in depletion (GMD) and that in weak inversion (GMW) decrease. It is found that ΔGMD and ΔGMW each have a linear relationship with the n-th power of stress time (tn) in a dual-log coordinate: ΔGMD ∝ tn, ΔGMD ∝ tn (n = 0.25). During the alternate stress, the injected holes neutralize QL induced by the previous EIS. This neutralization makes the effective VD restore to the initial value and then the IGD peak recovers completely. Yet the threshold voltage recovery is incomplete due to the trapped electron located over the channel (QC). As a result, GMW only recovers to circa 50% of the initial value after the hole-injection-stress (HIS). Instead, GMD almost recovers. The relevant mechanisms are given in detail. (interdisciplinary physics and related areas of science and technology)