Lateral PIN (p-MoTe₂/Intrinsic-MoTe₂/n-MoTe₂) Homojunction Photodiodes

The construction of high-speed electronic devices that can be integrated using a single two-dimensional (2D) semiconductor with high performance remains challenging due to the absence of locally selective doping methods. In this study, we have demonstrated that the selective opposite polarities (p-type or n-type) from an intrinsic 2H-MoTe2 field-effect transistor (FET) can be configured through carrier type band modulation in molybdenum ditelluride (MoTe2) caused by the charge storage interface in MoTe2/BN vdW heterostructures upon UV illumination with electrostatic gate bias. With this approach, we demonstrate a lateral p-i-n homojunction diode (p-MoTe2/intrinsic-MoTe2/n-MoTe2) using a single two-dimensional semiconductor (2H-MoTe2) where an intrinsic FET (i-type region) is sandwiched between p- and n-type FETs. Electrical performance of such a p-i-n diode demonstrates an ideal rectifying behavior with a rectification ratio (If/Ir) of up to ∼1.4 × 106 at zero gate bias with an ideal value of the ideality factor of nearly ∼1. To support optoelectrical doping, Kelvin probe force microscopy (KPFM) measurements are performed where p- and n-type MoTe2 channels show work function values of ∼5.0 and ∼ 4.55 eV, respectively, with a built-in potential of ∼450 mV. In the photovoltaic mode, the p-i-n diode shows excellent photodetection properties under an illumination of 600 nm, a maximum value of responsivity of 1.10 A/W, and a specific detectivity value of 3.0 × 1012 Jones. The device shows ultrafast photoresponses, where the response speed (τr/τf) is estimated to be 10/20 ns. The proposed research offers an opportunity for creating stable p-i-n homojunction diodes for high-speed electronics with low power consumption using 2D materials.