WSe₂ Homojunction p–n Diode Formed by Photoinduced Activation of Mid-Gap Defect States in Boron Nitride

Abstract

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.

Highly Efficient, Surface Ligand Modified Quantum Dot Light‐Emitting Diodes Driven by Type‐Controllable MoTe2 Thin Film Transistors via Electron Charge Enhancer

“…As a result, a clear type conversion of MoTe 2 TFTs without degradation of electrical properties was obtained, and both n‐type and p‐type MoTe 2 TFTs demonstrated a stable QLED‐operation. This successful type conversion result can be effectively utilized to realize the fundamental and important device application based on MoTe 2 such as p–n diode and complementary inverters, [ 28–33 ] without structural change or additional layer. Moreover, fabricated MoTe 2 TFTs exhibited excellent suppression of photocurrents under UV–near‐infrared (NIR) region, showing a unique advantage for the applications such as display backplane transistors as well as light‐to‐frequency conversion circuits, as compared to other TMDCs and conventional Si materials.…”

Controlling relaxation dynamics of excitonic states in monolayer transition metal dichalcogenides WS2 through interface engineering

“…The output curves under different back-gate voltages confirm effective tuning by back-gating on the background carrier concentration in WS2. The induced carrier concentration ne by the back-gate can be calculated by the relation ne = Cg(VG-Vth)/e, where VG is the bake-gate voltage, Vth is the threshold voltage, e is the electronic charge and Cg is the combined gate capacitance [23]. For the h-BN flakes with a thickness of 32 nm and the SiO2 film of 285 nm, the combined gate capacitance is ~1.09×10 -8 F/cm 2 , and the induced doping carrier concentration can be evaluated to be ~1.64×10 12 cm -2 at 50 V. Also, we have fabricated controlled back-gated devices of monolayer WS2 deposited on SiO2/Si substrate to compare the effects of different interfaces (See Supplementary).…”

Effect of an optimal oxide layer on the efficiency of graphene‐silicon Schottky junction solar cell

“…The work function of any sample can be calculated by the following relation. [36][37][38] Contact potential difference CPD…”