All 2D Heterostructure Tunnel Field-Effect Transistors: Impact of Band Alignment and Heterointerface Quality

Abstract

Van der Waals heterostructures are the ideal material platform for tunnel field effect transistors (TFETs) because a band-to-band tunneling (BTBT) dominant current is feasible at room temperature (RT) due to ideal, dangling bond free heterointerfaces. However, achieving subthreshold swing (SS) values lower than 60 mVdec-1 of the Boltzmann limit is still challenging. In this work, we systematically studied the band alignment and heterointerface quality in n-MoS2 channel heterostructure TFETs. By selecting a p +-MoS2 source with a sufficiently high doping level, stable gate modulation to a type III band alignment was achieved regardless of the number of MoS2 channel layers. For the gate stack formation, it was found that the deposition of Al2O3 as the top gate introduces defect states for the generation current under reverse bias, while the integration of an h-BN top gate provides a defect-free, clean interface, resulting in the BTBT dominant current even at RT. All 2D heterostructure TFETs produced by combining the type III n-MoS2/p +-MoS2 heterostructure with the h-BN top gate insulator resulted in low SS values at RT.

Intrinsic Electronic Transport Properties and Carrier Densities in PtS2 and SnSe2: Exploration of n+‐Source for 2D Tunnel FETs

“…The band alignment of the heterostructure gradually changes from type II to type III but does not reach type III at V D = 0 V because V BTBT does not reach 0 V, which can be compared with Figure 3a in ref. [10]. The band alignment at V D = 0 V cannot be changed from type II to type III by only using the V G because E F of the PtS 2 source as well as the WSe 2 channel is also modulated by V G due to the low n. The transfer characteristic of the heterostructure TFET at the reverse bias of −2 V at RT is shown in Figure 4e.…”

“…[4][5][6][7] Here, 2D materials provide an ideal platform for TFETs because the dangling-bond-free van der Waals (vdW) heterointerface minimizes carrier generation and the short tunnel distance at the vdW interface increases the on current. [8,9] To date, n-type 2D-TFETs have been mainly investigated because degenerately doped p + -2D materials, such as Nb-doped p + -MoS 2 , [10,11] intrinsic p + -black phosphorus (BP), [12][13][14][15] and externally doped p + -WSe 2 , [16,17] are available as source materials. Degenerately doped source materials are indispensable for TFETs because their high carrier densities afford sharp SS values as well as high on current by modulating the band alignment only in the channel region, not in the source region.…”

Spectrum adapted expectation-conditional maximization algorithm for extending high–throughput peak separation method in XPS analysis

“…Proposed method was applied to the W 4 f core-level spectrum and the C 1s core-level photoelectron spectrum. The W 4 f core-level spectrum was taken by a mechanically exfoliated WSe 2 sheet in a 2D heterostructure tunnel field effect transistor [32]. Also, the C 1s core-level photoelectron spectrum was taken by a graphene sheet on a 90 nm SiO 2 /p + -Si(100) substrate [33].…”

Science of 2.5 dimensional materials: paradigm shift of materials science toward future social innovation

“…Reproduced with permission from American Chemical Society (modified from ref. [ 14 ]). (d) Schematic illustration of a BP/MoSe 2 heterojunction device and response of three sensors as a function of NO 2 gas concentration.…”

“…TFETs are more feasible for 2.5D materials because the device design, which is based on the band-to-band tunnelling (BTBT), can be easily implemented by the characteristics of 2D materials – the shorter tunnelling distance owing to the vdW gap and the strong gate controllability owing to the atomically thin channel. All-2D-heterostructure TFETs (which may be called 2.5D-TFETs) produced by combining a type III n -MoS 2 / p + -MoS 2 heterostructure with a hBN top gate insulator resulted in SS values lower than 60 mVdec −1 at room temperature, as shown in Figure 10(c) [ 14 ]. Further reductions in SS values and higher on-currents are possible when the entire hetero-interface is more rigorously controlled [ 165 ].…”