Implementing Lateral MoSe₂ P–N Homojunction by Efficient Carrier-Type Modulation

High-performance p–n junctions based on atomically thin two-dimensional (2D) materials are the fundamental building blocks for many nanoscale functional devices that are ideal for future electronic and optoelectronic applications. The lateral p–n homojunctions with conveniently tunable band offset outperform vertically stacked ones, however, the realization of lateral p–n homojunctions usually require efficient carrier-type modulation in a single 2D material flake, which remains a tech challenge. In this work, we have realized effective carrier-type modulation in a single MoSe2 flake, and thus, a lateral MoSe2 p–n homojunction is achieved by sequential treatment of air rapid thermal annealing and triphenylphosphine (PPh3) solution coating. The rapid thermal annealing modulates MoSe2 flakes from naturally n-type doping to degenerated p-type doping and improves the hole mobility of the MoSe2 field effect transistors from 0.2 to 71.5 cm2·V–1·s–1. Meanwhile, the n-doping of MoSe2 is increased by drop-coating PPh3 solution on the MoSe2 surface with increased electron mobility from 78.6 to 412.8 cm2·V–1·s–1. The as-fabricated lateral MoSe2 p–n homojunction presents a high rectification ratio of 104, an ideality factor of 1.2, and enhanced photoresponse of 1.3 A·W–1 to visible light. This efficient carrier-type modulation within a single MoSe2 flake has potential for use in various functional devices.