Impact of interfacial charges on analog and RF performance of Mg2Si source heterojunction double-gate tunnel field effect transistor

Abstract

Tunnel field effect transistors (TFETs) have proved themselves as a better choice for the replacement of MOSFET due to provision of scalability and possibility of better realization of goal to achieve subthreshold swing less than 60 mV/decade. Challenge of lower ON current in conventional TFET has been overcome by a heterojunction double-gate (DG) TFET structure in which a low bandgap material, magnesium silicide (Mg2Si) is implemented as source region. There is dire need to determine the reliability of such device under various constraints to optimize them for low-power and high-speed applications. Therefore, in this paper, authors examine the device reliability by investigating the analog/RF performance of Mg2Si source heterojunction double-gate TFET (MSH-DG-TFET) under the influence of interface trap charge polarity and density. This reliability analysis is accomplished by including the effect of trap charges (both positive interface charges, i.e., donors and negative interface charges, i.e., acceptors) at Si/SiO2 interface. Presence of these trapped acceptor and donor charges at Si/SiO2 interface modifies the flat-band voltage which in turn alters the performance of the device. It is revealed that for positive trap charge density of 1 × 1012 cm−2, the leakage current or off-state current of MSH-DG-TFET drastically increases from an order of 10–18 to 10–14 A/µm, thus degrading the performance. Further, presence of negative trap charges at interface tends to enhance the flat-band voltage that translates to the higher gate bias to turn the device ON. Results reveal that impact of positive interface charges is more pernicious on the device performance as compared to the negative interface charges. Thus, MSH-DG-TFET is susceptible to the donor traps existing at Si/SiO2 in comparison with the acceptor traps. Studies carried out may prove to be very useful for future research work in suggesting better TFET structures comprising of Mg2Si as source.