Si-based hetero-material-gate tunnel field effect transistor: Analytical model and simulation

Abstract

In this paper, we present an analytical model of silicon-based hetero-material-gate (HMG) tunnel field effect transistor (TFET)_ This model includes the calculation of electric potential, electric field and band-to-band tunneling rate.Electrical characteristics of the HMG TFET can be accurately described by this model. The electrical behavior of the HMG TFET obtained by the analytical model is compared with the numerical simulation results, and shows excellent agreement. It is demonstrated that the HMG TFET has superior electrical performance than single-materia I-gate TFET. I. I NTRODUCTION Recently, tunnel field effect transistor (TFET) has attracted lots of attention for the ultra-low power application [1]- [3]. Theoretical and experimental results showed that TFET devices can provide a subthreshold swing (SS) lower than 60mV/dec at room temperature [4]-[8], and they can achieve a higher ratio between on-and off-state currents compared to MOSFET devices. However, the trade-off between SS and the on-state current (Ion) becomes an obstacle for the development of TFET devices [9]. To improve the Ion current and reduce the average SS simultaneously, a new structure named hetero-material-gate (HMG) TFET was proposed [10], [11]. This device has two materials in the gate with different workfunctions. Due to the special gate structure, the energy band profile of the HMG TFET is modulated, and a local minimum in conduction band is formed. Previous simulation results showed this band profile modulation (BPM) effect can lead to an abrupt switching behavior and an improved Ion current of TFETs [12]. Based on this design principle, some novel devices were also proposed [13], [14].Another key point in TFET research is the physical-based analytical modeling. The analytical model not only boosts the computation efficiency but also provides the understanding of the TFET behavior. In previous literature, some one dimensional (lD) analytical calculations have been reported [15]-[18]. However, duo to the natural behavior of the Manuscript ).quantum tunneling, the 2D model is needed to describe the characteristics of the TFETs. A few 2D analytical modeling results have been developed, such as double-gate structures [19] and single-gate silicon on insulator (SOl) TFETs [20]. In this paper, an analytical model of the HMG TFET is developed, considering the electric field and energy band profile. The accuracy of the model is verified by comparing the model results with the 2D numerical simulation results. The electrical performance of the HMG TFET is examined by the analytical model and numerical simulation in detail. II. A NALYTICAL M ODEL D ESCRIPTION

Drain Current Modeling of Tunnel FET using Simpson’s Rule

“…Several numerical models for TFET drain current [9] [12] reported in literature are computationally complex and hence it is inefficient to do circuit simulations using these models. Investigations on various modeling approaches [13] - [17] point out the need to develop an accurate and computationally efficient analytical model for drain current of TFET.…”