Polarization‐Induced Band‐Alignment Transition and Nonvolatile p‐n Junctions in 2D Van der Waals Heterostructures

Abstract

optoelectronic devices. The atom-scale thickness and the absence of surface dangling bonds enable them significant advantage for the electrostatic control and van der Waals (vdW) integration, which is essential for the realization of functional devices with scaling dimensions and ultralow off-state power consumption. [5,6] The formation of p-n junctions is a fundamental step for the realization of 2D semiconductor devices used in transistors, memories, photodetectors, solar cells, and light-emitting diodes. [7,8] The doping via the intentional introduction of charged impurities into a semiconductor host lattice is the most common way to create excessive electrons or holes for the realization of p-n junctions. [9] However, implementing this method in 2D semiconductors remains a large challenge because their ultrathin crystal structure and limited physical space are difficult to ensure the incorporation of sufficient impurities without serious structural damage. [10] Great efforts have been devoted to exploiting efficient doping strategies for the manipulation of the type and concentration of charged carriers, such as electrostatic doping, [11] chemical intercalation, [12] surface charge transfer, [13] photo-induced doping, [14] and electron beam irradiation. [15] Among these doping approaches, the chemical intercalation and surface charge transfer are capable of inducing high carrier densities, but they inevitably introduce unintentional chemical species and structural disorder that degrade device mobility. [16] The electron beam irradiation and photo-induce doping strategies can be used to modulate the charge carriers (including type and concentration) with high spatial resolution, but they easily induce the degradation of 2D materials due to the formation of defective structures induced by the high energy of irradiation. [17] The gate-tuned electrostatic doping is widely considered as an efficient way to tune the charge carriers for the realization of p-n junctions in 2D semiconductors without introducing defects or impurities. However, this approach requires the introduction of an external voltage to maintain the carrier type, making that the doping process is volatile. Therefore, the development of nondestructive doping way to produce p-n junctions in atomically thin semiconductors is strongly desired.An alternative strategy is the doping modulation via intrinsic spontaneous polarization that takes advantage of nonvolatile electrostatic field induced by polar materials (e.g., ferroelectrics) at an interface. This doping strategy does not require 2D van der Waals (vdW) p-n junctions based on vertically stacked atomically thin semiconductor materials have shown tremendous potential in highperformance integrated electronics and optoelectronics. However, unlike traditional semiconductors, the conventional doping methods to achieve p-type and n-type doping in 2D semiconductors remain a large challenge due to their ultrathin structures with limited physical space. Here, by means of density functional theory computat...

Domain nucleation kinetics and polarization-texture-dependent electronic properties in two-dimensional α-In2Se3 ferroelectrics

“…The OOP localization of the CBM and VBM states arises from the polarization-induced band bending. 38,52 For the case of R up = 18.75%, the bands of the P down and P up regions are not degenerate (Fig. 4b).…”

“…Our recent studies have revealed that the electronic structures and carrier density of α-In 2 Se 3 depend on the polarization orientation and phase structure. 38,39 Despite these advances, it remains challenging to understand the domain switching dynamics in α-In 2 Se 3 , including the domain nucleation and growth process, since the evolution of the FE domains usually takes place on very short timescales at the atomic scale. Moreover, a qualitative relationship between the electronic structures and domain textures of α-In 2 Se 3 ferroelectrics remains unexplored.…”

g-ZnO/Si9C15: a S-scheme heterojunction with high carrier mobility for photo-electro catalysis of water splitting

“…Cao et al 41 reported 2D WSeTe/XS 2 (X = Hf, Sn, and Zr) vdW heterojunctions, and constructed six different structural models for the WSeTe/HfS 2 bilayer, the WSeTe/SnS 2 bilayer, and the WSeTe/ZrS 2 bilayer, respectively. Yang et al 42 considered six stacking configurations of MoSe 2 /GaN interfaces to confirm the most stable heterojunction model, and obtained them through the translation method. Yu et al 43 considered multiple atomic coincidence patterns when constructing the Janus MoSSe/WX 2 (X = S and Se) vdW heterojunction models.…”

The tunable interface charge transfer by polarization in two dimensional polar Al2O3/MoSO heterostructures

“…Usually, the situation is that one layer gets electrons and another layer loses electrons. Previous research studies 24–86 on 2D vdWs semiconductor heterostructures with type-II band alignment are listed in Table 1. Some of them have been proved theoretically to be Z-scheme photocatalysts for water-splitting.…”