High‐Responsivity Graphene/4H‐SiC Ultraviolet Photodetector Based on a Planar Junction Formed by the Dual Modulation of Electric and Light Fields

Abstract

Ultraviolet (UV) photodetectors have been fabricated on a graphene/4H-SiC wafer. In this device, the electrical doping in the graphene layer, under the gate, is realized by changing the gate voltage while the optical doping in the graphene layer outside the gate region is realized through the photogenerated carrier injection from SiC, by laser excitation at 325 nm. This kind of dual modulation of optical and electric fields ultimately results in the formation of a planar n-p-n or n-n-n junction in the graphene layer. The photoresponse results demonstrate that the planar n-p-n junction is formed at the negative gate voltage, and facilitates negative photoconductivity. The n-n-n junction is formed at the positive gate voltage and facilitates normal photoconductivity. The maximum responsivity, which is attributable to the high photoconductive gain in the planar n-n-n junction, is 254.1A W −1 , at drain-source voltage of −3 V and gate-source voltage of 3 V. Based on these results, the estimated lifetime of the electrons in the graphene channel extends greatly to more than four orders of magnitude longer than that in the isolated graphene. The above results prove that this graphene/4H-SiC combined structure possesses great potential in practical UV-detection applications.

p-GaSe/n-Ga2O3 van der Waals Heterostructure Photodetector at Solar-Blind Wavelengths with Ultrahigh Responsivity and Detectivity

“…Integration of wide E g semiconductors with vdW s layered materials has shed new light on designing promising functional electronics and optoelectronics such as blue and UV LEDs, UV PDs, and high-power electronics. − Especially, the atomically thin layers and clean interfaces will enable fast transfer of photogenerated electron–hole across the interfacial layer. Most pioneer works focused on vdW Schottky barrier junctions, including graphene/SiC, graphene/GaN, graphene/ZnO, and graphene/Ga 2 O 3 , all demonstrating improved photoresponse characteristics. − Until now very few studies have been carried out to construct Ga 2 O 3 -based mixed-dimensional pn vdW heterostructures. Therefore, by substituting graphene with p -type 2D semiconductors, the construction of vdW pn heterojunctions could enable a promising approach to further promote the carriers separation and suppress the dark current for the device.…”

Gate-Controlled NiO/Graphene/4H-SiC Double Schottky Barrier Heterojunction Based on a Metal-Oxide-Semiconductor Structure for Dual-Mode and Wide Range Ultraviolet Detection

“…In addition, the specific detectivity ( D *) of the device was also calculated by eq , where e is the elementary charge. The device also had a high detectivity of 1.07 × 10 13 Jones (Figure b).…”

“…Normally, thin semitransparent metal electrodes are employed in Schottky junctions to obtain a wider light reception area, , but the light is partially absorbed. However, graphene, a material with excellent transparency and mobility, has proven to be a viable alternative to metal electrodes in heterojunctions. − UV photodetectors made with a graphene/WBS heterojunction have been frequently reported in recent years. − These devices worked in either photoconductive mode with a highly conductive graphene channel or Schottky junction mode, which could provide high responsivity or detectivity, respectively. The Schottky junction device has a much lower dark current than the photoconductive device, but it is difficult to boost the responsivity significantly due to the lack of gain.…”

Two-Dimensional Field-Effect Transistor Sensors: The Road toward Commercialization

“…Sensing events and signal conversion normally occur at heterogeneous interfaces. ,, In the field of FETs, 2D materials restrain charge flow solely on the surface, which directly exposes it to the environment and is entirely located at the interfaces of signal acquisition and conversion, leading to rapid and sensitive response upon exposure to the outer stimuli. ,, In detail, the advantages of 2D FET sensors are attributed to at least three aspects: (i) The free dangling bonds enable 2D materials to construct functional heterostructures with ideal vdW interfaces readily. − It reduces the scattering center, which is key to maintain their attractive electronic properties (e.g., high carrier mobility) even after different device fabrication and modification processes . (ii) The atomic thickness ensures direct exposure of the channel to functional interfaces and/or external environments, leading to a rapid response to foreign stimuli with ultrahigh sensitivity. − (iii) The large surface-to-volume ratio provides abundant modification sites for anchoring specific receptors, which ensures the sensitivity and specificity upon specific perturbations. − This section clarifies the motivation of using 2D materials, the concepts, and the fundamentals of the 2D FET sensors.…”