P‐Type 2D Semiconductors for Future Electronics

Abstract

Abstract2D semiconductors represent one of the best candidates to extend Moore's law for their superiorities, such as keeping high carrier mobility and remarkable gate‐control capability at atomic thickness. Complementary transistors and van der Waals junctions are critical in realizing 2D semiconductors‐based integrated circuits suitable for future electronics. N‐type 2D semiconductors have been reported predominantly for the strong electron doping caused by interfacial charge impurities and internal structural defects. By contrast, superior and reliable p‐type 2D semiconductors with holes as majority carriers are still scarce. Not only that, but some critical issues have not been adequately addressed, including their controlled synthesis in wafer size and high quality, defect and carrier modulation, optimization of interface and contact, and application in high‐speed and low‐power integrated devices. Here the material toolkit, synthesis strategies, device basics, and digital electronics closely related to p‐type 2D semiconductors are reviewed. Their opportunities, challenges, and prospects for future electronic applications are also discussed, which would be promising or even shining in the post‐Moore era.

Wearable Sensors Based on Atomically Thin P‐Type Semiconductors

“…[201] To address this issue, ambipolar 2D semiconductors, such as WSe 2 , MoTe 2 , etc., establish strong p-type conduction. [16,202,203] Typically, a split-gate design creates a p-n junction in a single 2D material layer. [202][203][204] Baugher et al [202] created zones of different conduction types inside a single WSe 2 nanosheet using two local gates.…”

“…[ 201 ] To address this issue, ambipolar 2D semiconductors, such as WSe 2 , MoTe 2 , etc., establish strong p‐ type conduction. [ 16,202,203 ] Typically, a split‐gate design creates a p–n junction in a single 2D material layer. [ 202–204 ] Baugher et al.…”

“…[14] However, most reported 2D materials are n-type due to the strong electron doping effect of interfacial charge impurities and intrinsic defects. [15,16] Constructing complementary electronic devices and high-performance wearable sensors requires p-type 2D semiconductors. [9,[17][18][19][20][21][22] P-type 2D semiconductors are reported to show higher electrocatalytic performance in oxidative reactions compared to their n-type counterparts because their fermi level lies closer to the conduction band edge.…”

“…[29] One major issue with the p-type conduction of 2D materials is the fermi level pinning at the metal/2D materials interface, typically prohibiting the injection of holes. [15,16,30] Moreover, only a few intrinsic p-type 2D semiconductors have been reported, [17,[33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] such as WSe 2 , [31] black phosphorus, [32] tellurene, [33] MnS, [17] and Ga 2 S 3 , [18] etc., where many of them (e.g., black phosphorus) suffer from ambient stability, which hinders their applications on wearables. To meet these demands and address related issues, intensive efforts have been devoted to realizing p-and n-type 2D semiconductors, with even more attention on p-type 2D semiconductors than their n-type counterparts (Figure 1b).…”

“…While previous reviews have discussed materials, manufacturing, and device‐level research for 2D material‐based wearables, few have focused on 2D p‐ type semiconductors, and those that have often relate to materials [ 15 ] or general electronic applications. [ 16 ] This review provides a comprehensive account of current developments in 2D p‐ type semiconductor‐based wearable sensors to address this gap. The characteristics, fabrication, and functioning processes of the state‐of‐the‐art 2D p‐ type semiconductor wearable sensors and insights into how p‐ type behavior impacts sensor performance are reviewed.…”