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 cm(2).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 cm(2).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.