A single nanoflake lateral p–n diode (in-plane) based on a two-dimensional material can facilitate electronic architecture miniaturization. Here, a novel lateral homojunction p–n diode of a single WSe2 nanoflake is fabricated by photoinduced doping via optical excitation of defect states in an h-BN nanoflake upon illumination. This lateral diode is fabricated using a mechanical exfoliation technique by stacking the WSe2 nanoflake partially on the h-BN and Si substrates. The carrier type in the part of the WSe2 film on the h-BN substrate is inverted and a built-in potential difference is formed, ranging from 5.0 to 4.50 eV, which is measured by Kelvin probe force microscopy. The contact potential difference across the junction of p-WSe2 and n-WSe2 is found to be ∼492 mV. The lateral diode shows an excellent rectification ratio, up to ∼3.9 × 104, with an ideality factor of ∼1.1. A typical self-biased photovoltaic behavior is observed at the p–n junction upon the illumination of incident light, that is, a positive open-circuit voltage (V oc) is generated, that is, voltage obtained (at I ds = 0 V), and also a negative short-circuit current (I sc) is generated, that is, current obtained (at V ds = 0 V). The presence of built-in potential in the proposed homojunction diode establishes I sc and V oc upon illumination, which can be implemented for a self-powered photovoltaic system in future electronics. The proposed doping technique can be effectively applied to form planar homojunction devices without a photoresist for future electronic and optoelectronic applications.

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 (I f/I r) 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.

Ultrathin and light heterojunction bipolar transistors based on two-dimensional (2D) layered materials with flexible semiconducting properties have been considered for several electronic applications. In this paper, a van der Waals p-BP/n-MoS 2 /p-BP BJT is demonstrated. It is fabricated using mechanical exfoliation, where a dry transfer technique is used to stack a vertical double heterojunction. The device structure includes nanoflakes of black phosphorus (BP) and MoS 2 . The current-voltage characteristics of the common-emitter and common-base configurations are examined. These p-BP/n-MoS 2 /p-BP bipolar transistors exhibit current-voltage characteristics similar to those of conventional p-n-p bipolar transistors. Devices with thin MoS 2 layers show good saturation current-voltage characteristics, and a maximum common-emitter current gain (β = I C /I B ) of approximately 10.1 is obtained at room temperature (300 K). Furthermore, the thickness dependence of the base region (n-MoS 2 ) is investigated for the common-emitter output electrical characteristics (V CE − I C ) of a double heterojunction bipolar transistor in which the emitter is grounded. The collector current decreases as the thickness of n-MoS 2 is increased. This study can pave the way for the application of 2D materials as controllable amplifiers in flexible electronics.

The main challenge encountered by most 2D materials for their use in non-volatile memory technology is their low Ron/off ratio.