Читать книгу Electrical and Electronic Devices, Circuits, and Materials - Группа авторов - Страница 26

Since the last few decades, the electronics industry has enjoyed conventional MOSFET due to aggressive scaling property. This “aggressive scaling” progress concept with conventional MOSFET, has also produced numerous challenges briefly known as short channel effects (SCEs) [1–5]. In addition, the current mechanism in MOSFETs is controlled by a drift-diffusion, a conventional charge transport phenomenon popularly known as thermionic emission of charge carriers in ultra-scaled MOSFETs [3–5]. The drift-diffusion of high-energy charge carriers in ultra-scaled MOSFETs follow the Fermi–Dirac distribution and hence have an energy slope of kT (where k is the Boltzmann constant, T is the absolute temperature). This is a technical reason that conventional MOSFET causes subthreshold slope limitation, SS > 60 mV/decade at room temperature. This technical barrier in the progress path of electronic industry with conventional MOSFETs causes a bottleneck issue for semiconductor players. In addition, a quantum transport mechanism known as tunneling between band-to-band (B2B) in the ultra-scaled field effect devices, does not suffer such limitations imposed by the Boltzmann [3–8]. This transport mechanism allow further scaling of FET devices with scaled power supply (VDD) [9–12], which makes tunneling device the most promising alternative for the conventional MOSFETs for low-power circuit and system applications.

Unlike conventional MOSFETs, TFETs are basically an asymmetrical source/drain highly doped FET device. The basic structure of TFET device is derived and developed by p-i-n diode [10, 11], containing two heavily doped degenerated semiconductor “p” and “n” regions and lightly doped intrinsic “i” region, respectively. It is commonly operated in reverse biased condition. The current generation in tunneling devices is enabled by the band-to-band (B2B) tunneling mechanism between the source to drain region via channel [13–17].

However, the lower switching current due to limited tunneling charge carriers in tunnel FET devices than conventional MOSFETs has become problematic for solving limitations of conventional MOSETs [3–8]. To obtain the improved electrical characteristics in terms of current efficiency (ION), leakage current (IOFF), subthreshold slope (SS), transconductance (gm), switching response time etc., several ideas have been proposed by scientists and semiconductor players. Gate dielectric and bandgap engineering were the most popular key ideas [18–25]. As per requirements and state-of-the-art modern ultra-low-power electronics, this chapter is dedicated to double gate tunnel FET (DG -TFET ), circuit and system design. In this chapter, we explore the idea of high-k dielectric engineering as well as band engineering concept with DG -TFET. A detailed investigation has been done for the requirements for ultra-low-power circuit and system design based on DG -TFET.