Asymmetric Double-Gate β-Ga 2 O 3 Nanomembrane Field-Effect Transistor for Energy-Efficient Power Devices

Abstract

DOI: 10.1002/aelm.201800938 such as silicon carbide (SiC) and gallium nitride (GaN).[4,5] In addition, costeffective high quality β-Ga2O3 wafer from bulk single crystal obtained from meltgrowth methods provides a significant advantage over other wideband gap materials because SiC and GaN wafers require expensive high temperature vacuum synthesis.[6–9] Furthermore, β-Ga2O3 exhibits a comparable Johnson FOM intended for high-frequency operation in spite of its relatively lower saturation velocity.[10,11] Aforementioned unique properties of β-Ga2O3 have facilitated intensive research efforts for high-power and radiofrequency (RF) electronics, and various device structures have been demonstrated as a building block such as Schottky barrier diode (SBD), metal-oxide field-effect transistors (MOSFET), metal-semiconductor field-effect transistors (MESFET), and even heterostructures with low dimensional materials.[12–16] In particular, MESFET not only eliminates problems with oxide reliability and interface traps but also provides better size scaling, and thus β-Ga2O3 MESFET is a promising structure for the applications.[6,17] On the other hand, backand top-gate modulation of β-Ga2O3 MOSFET is reported, showing that the electrical characteristics can be beneficially tuned.[18] In this work, we fabricate asymmetric double-gate (DG) β-Ga2O3 nanomembrane FET having bottom-gate (BG) MOSFET and top-gate (TG) MESFET. Specifically, a high crystal quality β-Ga2O3(100) channel is obtained from a bulk β-Ga2O3 crystal substrate using a mechanical exfoliation method. The asymmetric DG β-Ga2O3 FET is comprised of a lateral Schottky barrier diode, BG-MOSFET, and TG-MESFET, which are characterized separately to validate and compare their electrical performance. Benefiting from performance modulations of the individual devices, high performance asymmetric DG β-Ga2O3 FET is achieved for energy-efficient high voltage and frequency devices. Moreover, detailed analysis has been conducted to assess the modulation of electrical properties as well as enhanced performance based on energy band model and TCAD simulations.