Advanced Heterostructure based Nano Scale MOSFETs

Prof. (Dr.) Chandan Kumar Sarkar
Professor, Dept of Electronics and Telecommunication Engineering,
Jadavpur University, Kolkata

Abstract -  

                   The MOSFET scaling, which continued for last four decades, offers a unique feature that its performance enhances as the dimensions reduces. However, as MOSFETs are scaled to sub 20 nm dimensions, it becomes very difficult to maintain the necessary device performance, due to significantly increased short channel effects (SCE), limitations of channel mobility, gate oxide scaling and parasitics. The potential remedy is to introduce a new channel material and advanced device structures. The new channel materials must have higher mobility and much higher velocity so that charge carriers can travel much faster than in silicon. The search has focused the attention on III–V compound semiconductors. Materials such as GaN, AlN, InN, GaAs, AlAs, InAs, InP, their ternary and quaternary alloys, combine the elements form columns III and V of the periodic table. The GaN and related alloys have many advantages including high breakdown field, high and direct bandgap and relatively good lattice matching between AlGaN/GaN, AlInN/GaN. The existence of strong polarization fields within the GaN based heterostructures offers very high sheet carrier concentration  (> 1013cm−2) in the 2DEG channel without any intentional doping. The polarization effect in GaN is two-fold: spontaneous polarization and strain-induced piezoelectric polarization. The other aspect to overcome the scaling related problem is to use advanced device structure. In this work, the intent is to arrive at a novel device structure that takes into account both high performance (as in HEMT), and low leakage and reduced SCE (as in DG MOSFET). The new III–V heterostructure MOSFET (MOS-HEMT) device aims to achieve high ON current from HEMT like mechanism, and good OFF state control by DG MOSFET like mechanism. Here the DC, Analog and RF performance of DG Underlap AlInN/GaN MOS-HEMT is presented and compared with HEMT device.