Modelling and simulation of 2d aluminium-doped silicene transport properties in field-effect transistors

Abstract

One of the more-than-Moore approaches is to use two-dimensional (2D) silicene as the channel in a transistor. Silicene shares outstanding electronic properties with graphene, yet provides an added advantage in terms of its compatibility with silicon (Si) wafer technology. However, pristine silicene has an almost zero bandgap at the Dirac point, which inhibits its potential as a field-effect transistor (FET). This study focused on the modelling and simulation of bandgap-engineered silicene FETs from material level to device level. Concerning material-level modelling, the nearest neighbour tight-binding (NNTB) model was used to obtain the dispersion (E-k) relation and density of states (DOS) of pristine silicene. A bandgap was then induced in silicene using aluminium (Al) substitutional doping at a uniform concentration to produce the AlSi3 nanosheet. Applying this uniform doping technique, the locations of dopants are not restricted, unlike selective substitutional doping where the electronic properties vary with the doping locations. Al is among the most promising dopants for silicene because it does not distort the honeycomb lattice arrangement. The E-k relation and DOS of AlSi3 were also obtained. Subsequently, the DOS and Fermi- Dirac probability distributions were used to compute the carrier transport properties of AlSi3. Regarding the device-level modelling, the top-of-the-barrier (TOB) ballistic nanotransistor model was employed to simulate the proposed AlSi3 FET model in terms of its output characteristics (Ids - VDS) and transfer characteristics (Ids - Vgs). The device performance of the AlSi3 FET was evaluated by benchmarking against published results in terms of device metrics such as threshold voltage (Vth), drain-induced barrier lowering (DIBL), subthreshold swing (SS) and on-off current (IonI h f f ) ratio. The AlSi3 FET exhibits SS as low as 67.8 m V/dec, which is close to the ideal SS at room temperature (approximately 60m V | dec), DIBL of 48.2 m V| V , and Ion/ I of f ratio up to an order of five (approximately 2.6 x 105). The proposed AlSi3 FET outperforms the Si FinFET (SS and DIBL reduction of approximately 46 % and 32 %, respectively, and Ion/ I of f ratio improvement of approximately 102) and exhibits a device performance that is comparable to that of other low-dimensional materials. Subsequently, a SPICE model was created to facilitate further circuit-level simulation. This study demonstrates that AlSi3 is one of the most promising 2D materials for modern nanoelectronic applications.