Enhanced responsivity and detectivity of fast WSe2 phototransistor using electrostatically tunable in-plane lateral p-n homojunction

Abstract

Layered transition metal dichalcogenides have shown tremendous potential for photodetection due to their non-zero direct bandgaps, high light absorption coefficients and carrier mobilities, and ability to form atomically sharp and defect-free heterointerfaces. A critical and fundamental bottleneck in the realization of high performance detectors is their trap-dependent photoresponse that trades off responsivity with speed. This work demonstrates a facile method of attenuating this trade-off by nearly 2x through integration of a lateral, in-plane, electrostatically tunable p-n homojunction with a conventional WSe2 phototransistor. The tunable p-n junction allows modulation of the photocarrier population and width of the conducting channel independently from the phototransistor. Increased illumination current with the lateral p-n junction helps achieve responsivity enhancement upto 2.4x at nearly the same switching speed (14–16 µs) over a wide range of laser power (300 pW–33 nW). The added benefit of reduced dark current enhances specific detectivity (D*) by nearly 25x to yield a maximum measured flicker noise-limited D* of 1.1×1012 Jones. High responsivity of 170 A/W at 300 pW laser power along with the ability to detect sub-1 pW laser switching are demonstrated.

Wavelength‐Controlled Photocurrent Polarity Switching in BP‐MoS2 Heterostructure

“…This makes them an excellent choice for photodetection applications. Generally, the device architecture and choice of 2D materials in these heterostructures have been shown to enhance the positive photoconductance [ 1,11–14 ] (PPC) for application areas such as photodetectors [ 15 ] or optical memories. [ 16,17 ] However, some recent studies have also shown the possibility of realizing negative photoconductance [ 18–23 ] (NPC) in 2D material‐based devices.…”

Fluorinated Dielectrics‐Modulated Organic Phototransistors and Flexible Image Sensors

“…Photoresponsivity ( R ) is another key parameter for evaluating the performance of phototransistors. [ 37–39 ] (Figure S10b,e,h, Supporting Information) depicted the gate voltage‐dependent R when the devices were illuminated with various light intensities with V D fixed at −20 V. R as high as 7.64 × 10 2 , 1.64 × 10 4 , and 1.61 × 10 4 A W −1 for PI, ODA‐6FDA PI, and TFMB‐6FDA PI phototransistors, respectively, could be achieved at a light intensity of 0.028 mW cm −2 (Figure 4e), indicating that the excellent capability of photoelectric conversion of fluorinated PI devices, especially ODA‐6FDA PI devices. In addition, the special detectivity ( D * ) can be written as [ 40,41 ] $$\[ \begin{array}{*{20}{c}}{{D^ * } = R{{(S\Delta f)}^{1/2}}{{({i_{\rm{n}}})}^{ - 1}}}\end{array} \]$$where Δ f is the operation bandwidth and i n is the measured noise current.…”

Pulsed‐Laser‐Deposition Fabricated ZnIn2S4 Photodetectors with Excellent ON/OFF Switching Characteristics toward High‐Temperature‐Resistant Photodetection Applications

“…[2][3][4][5] However, photodetectors based on traditional 2DLMs also suffer from some tough challenges. To begin with, the 2D devices are commonly constructed by uncontrollable methods and typically only a single prototype device is available in most of the previous studies, [6][7][8][9][10][11] while the preparation of multiple optoelectronic devices within one chip has been challenging to realize yet, especially for the common micro-mechanical exfoliation and chemical vapor deposition (CVD) methods. However, onchip integration is an indispensable precondition for practical engineering applications.…”