Multifunctional van der Waals Broken‐Gap Heterojunction

Abstract

devices based on heterojunctions can exhibit diverse functionality upon stacked 2D materials with different electron affinities and different bandgaps. [4,[6][7][8] Accordingly, heterojunctions can be classified into three distinct types based on their band-structure alignment: straddlinggap (type-I), staggered-gap (type-II), and broken-gap (type-III). In particular, broken-gap heterojunctions are interesting as there is no overlap between the energy bands of the two stacked materials, resulting in some exotic phenomena. [9][10][11][12] As apparent in recent reports, [6,13] change in current-transport across broken-gap heterojunctions can only be achieved by varying the combination of 2D materials employed. Hence, the majority of reported electronic devices exhibit inadequate control of multifunctional operations across the particular broken-gap heterojunction being used. Thus, diverse current-transport across a broken-gap heterojunction appears to be a primarily material-dependent phenomenon. In this article, we demonstrate that a black phosphorus (BP)-based broken-gap heterojunction can exhibit tunable current-transport characteristics. To elucidate our findings, we have chosen BP/rhenium disulfide (ReS 2 ) van der Waals (vdW) heterostructures for the following reasons: i) In addition to having majority charge carriers of opposite polarity (i.e., p-type BP and n-type ReS 2 ), BP/ ReS 2 forms a type-III broken-gap alignment at the heterojunction (Figure 1) and ii) BP flake work function exhibits substantial dependence on the respective flake thickness (Figure 1). Moreover, BP electronic structure features a lone pair of electrons at each phosphorus atom, which can interact strongly with out-of-plane atoms. [14][15][16] Consequently, BP has the potential to exhibit higher out-of-plane conductivities compared to other 2D materials and could be useful to be employed in heterostructures where vertical transport is usually dominant. [17,18] An advantage over epitaxial thinfilm-based heterojunctions is that the vdW gap enables band alignment at the heterojunction without requiring a tunneling barrier. [12,19,20] Our results demonstrate that current-transport across a BP/ ReS 2 broken-gap heterojunction can be tuned in a controlled way to function as a current-rectifying p-n junction diode-Esaki diode-backward-rectifying diode-nonrectifying device by gradually increasing the BP layer thickness from 5 to 100 nm or more. This is explained by the emergence of various The finite energy band-offset that appears between band structures of employed materials in a broken-gap heterojunction exhibits several interesting phenomena. Here, by employing a black phosphorus (BP)/ rhenium disulfide (ReS 2 ) heterojunction, the tunability of the BP work function (Φ BP ) with variation in flake thickness is exploited in order to demonstrate that a BP-based broken-gap heterojunction can manifest diverse current-transport characteristics such as gate tunable rectifying p-n junction diodes, Esaki diodes, backward-rectifying diodes, and nonr...

Reconfigurable Logic‐in‐Memory and Multilingual Artificial Synapses Based on 2D Heterostructures

“…The E 2g peak at 152 cm −1 , A 1g peak at 212 cm −1 of ReS 2 can also be observed. Moreover, the Raman spectrum of the junction region is the superposition of the characteristic peaks of two materials, consistent with previous results . Figure 1e,f shows the drain current I d mapping of the BP/ReS 2 heterostructures as a function of drain and gate voltage at 300 K (Figure 1e) and 4.3 K (Figure 1f).…”

“…Moreover, the Raman spectrum of the junction region is the superposition of the characteristic peaks of two materials, consistent with previous results. [18,38,39] Figure 1e,f shows the drain current I d mapping of the BP/ReS 2 heterostructures as a function of drain and gate voltage at 300 K ( Figure 1e) and 4.3 K (Figure 1f). The drain voltage is applied on BP terminal from -3 to 3 V and the ReS 2 source terminal is always grounded.…”

Interlayer Band‐to‐Band Tunneling and Negative Differential Resistance in van der Waals BP/InSe Field‐Effect Transistors

“…For BP, the carrier concentration tends to increase from p = 3.9 × 10 15 cm −3 to p = 2.7 × 10 17 cm −3 with increasing the layer thickness from t BP < 10 nm to t BP > 50 nm. A similar p‐type doping of BP and dependence of the hole density on the BP layer thickness were reported before 40,41…”

Multifunctional black phosphorus/MoS2 van der Waals heterojunction

“…Zhang et al demonstrated type II MoTe 2 /MoS 2 vdW heterostructures that show interlayer optical transition for the creation of an infrared (IR) photodetector beyond the limits of the intrinsic band gap of the constituting material [10]. Srivastava et al reported binary and ternary inverters with multifunctionality using a p + -n-p junction comprising BP (38 nm)/ReS 2 /BP (5.8 nm) [11]. Similarly, MoS 2 /BP heterostructures have also been prepared and studied.…”