Gate-free tunable 2D/2D heterojunction composed of MoTe2 and 2D electron gas at the surface of KTaO3

Abstract

The hybrid integration of oxide two-dimensional electron gases (2DEGs) and 2D layered transition-metal dichalcogenides is expected to exhibit diverse physical phenomena, which cannot appear in either material alone. Here, we demonstrate a gate-free tunable 2D/2D heterojunction composed of MoTe2 and 2DEG at the surface of KTaO3. The combination of metallic MoTe2 and n-type 2DEG together forms a Schottky diode with a large on/off current ratio of 104 at room temperature. Moreover, the MoTe2/2DEG diode exhibits largely tunable electrical transport characteristics without gate voltages. By applying bias voltages, the diode shows tunable transport properties ranging from insulating to excellent rectifying behaviors. The bias-voltage-dependent modulation dominantly originates from the tunable Schottky barrier width controlled by the carrier density of the 2DEG. Our results pave a way for the development of 2D nanoelectronic devices such as multi-bit memories and bias sensors.