Tunnel FET RF Rectifier Design for Energy Harvesting Applications

Abstract

Radio-frequency (RF)-powered energy harvesting systems have offered new perspectives in various scientific and clinical applications such as health monitoring, bio-signal acquisition, and battery-less data-transceivers. In such applications, an RF rectifier with high sensitivity, high power conversion efficiency (PCE) is critical to enable the utilization of the ambient RF signal power. In this paper, we explore the high PCE advantage of the steep-slope III-V heterojunction tunnel field-effect transistor (HTFET) RF rectifiers over the Si FinFET baseline design for RF-powered battery-less systems. We investigate the device characteristics of HTFETs to improve the sensitivity and PCE of the RF rectifiers. Different topologies including the two-transistor (2-T) and four-transistor (4-T) complementary-HTFET designs, and the n-type HTFET-only designs are evaluated with design parameter optimizations to achieve high PCE and high sensitivity. The performance evaluation of the optimized 4-T cross-coupled HTFET rectifier has shown an over 50% PCE with an RF input power ranging from dBm to dBm, which significantly extends the RF input power range compared to the baseline Si FinFET design. A maximum PCE of 84% and 85% has been achieved in the proposed 4-T N-HTFET-only rectifier at dBm input power and the 4-T cross-coupled HTFET rectifier atdBm input power, respectively. The capability of obtaining a high PCE at a low RF input power range reveals the superiority of the HTFET RF rectifiers for battery-less energy harvesting applications.Index Terms-Energy harvesting, power conversion efficiency, radio-frequency (RF)-powered systems, RF rectifier, steep subthreshold slope, tunnel field-effect transistors (FETs), III-V semiconductor.

Insights Into Tunnel FET-Based Charge Pumps and Rectifiers for Energy Harvesting Applications

“…In [10] we have shown that a gate crosscoupled charge-pump topology with TFETs powered by a thermogenerator presents a peak power conversion efficiency (PCE) of 74% for a temperature variation of 1 K (Vin=80 mV). In another work, the authors have shown similar PCE improvements in RF passive rectifiers based on TFETs for input power levels below -30 dBm (typical far-field ambient RF-power) [11]. These results are highly motivating for several applications where the power requirements of external batteries are still mandatory to ensure a proper circuit operation.…”

“…This characteristic can result in switching nodes with transient "spikes", with voltage values above the power supply voltage and below ground. For TFET-based charge-pumps and rectifier, this behavior can induce an increased switching power as referred in [11].…”

“…In [11] the authors have shown by simulations that the inclusion of TFET devices in passive rectifiers can improve the efficiency at such low power levels compared to similar rectifiers designed with FinFET technology. The TFET-based gate cross-coupled rectifier (GCCR) presented in Fig.…”

“…This characteristic can result in switching nodes with transient "spikes", with voltage values above the power supply voltage and below ground. For TFET-based charge-pumps and rectifier, this behavior can induce an increased switching power as referred in [11].In [13], the authors have shown that in comparison with Sibased TFETs, the design of TFETs with III-V materials (low bandgap and low mass ) can mitigate the Miller capacitance effect due to the reduced density of states (DOS) of such materials. Therefore, TFETs designed with III-V materials are advantageous in comparison with Silicon devices for ultra-low power applications focused on energy-harvesting.…”

Online Power and Time Allocation in MIMO Uplink Transmissions Powered by RF Wireless Energy Transfer

“…The received RF signals cannot be converted into DC (i.e., energy transfer) if their power level is lower than the power sensitivity of an RF-DC circuit [19]. Thus, actually received energy would be much lower than the theoretically predicted amount, leading to a falsely higher data rate.…”