No abstract

No abstract

We fabricated metal–semiconductor–metal-structured β-Ga2O3 photodetectors using a plasma-assisted pulsed laser deposition system with various oxygen plasma radio frequency (RF) powers ranging from 0 to 100 W. All optoelectronic properties of the material were enhanced as the RF power increased. β-Ga2O3 photodetector with RF power of 100 W showed the best optoelectronic characteristics, such as photoresponsivity of 0.39 A/W, external quantum efficiency of 192.61%, and detectivity of 9.09 × 1013 cm Hz1/2/W. In addition, photo-switching analysis revealed the fastest photoresponse speeds (1.46 and 0.21 s) for on/off switching. These results originate from the decrease in the oxygen vacancy defect concentration in the β-Ga2O3 films by the oxygen RF power. Our results suggest that β-Ga2O3 photodetectors fabricated with oxygen plasma can optimize and improve the photodetection performance and can be applied for future deep ultraviolet detectors.

Two-dimensional (2D) materials, such as molybdenum disulfide (MoS2) of the transition metal dichalcogenides family, are widely investigated because of their outstanding electrical and optical properties. However, not much of the 2D materials research completed to date has covered large-area structures comprised of high-quality heterojunction diodes. We fabricated a large-area n-MoS2/p-Si heterojunction structure by sulfurization of MoOx film, which is thermally evaporated on p-type silicon substrate. The n-MoS2/p-Si structure possessed excellent diode characteristics such as ideality factor of 1.53 and rectification ratio in excess of 104. Photoresponsivity and detectivity of the diode showed up to 475 mA/W and 6.5 × 1011 Jones, respectively, in wavelength ranges from visible to near-infrared. The device appeared also the maximum external quantum efficiency of 72%. The rise and decay times of optical transient response were measured about 19.78 ms and 0.99 ms, respectively. These results suggest that the sulfurization process for large-area 2D heterojunction with MoS2 can be applicable to next-generation electronic and optoelectronic devices.

We demonstrate area-selective doping of MoS2 field-effect transistors (FET) using 1,2-dichloroethane (DCE) solution. In the device manufacturing process, area-selective chemical doping was used to implement contact engineering in the source/drain region. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy measurements were performed to confirm the blocked layer (BL) using a photoresist, which suppressed the doping effect of the DCE treatment. In the XPS results, the main core level of the MoS2 flake with BL did not shift, whereas that of the MoS2 flake without BL changed by approximately 0.24 eV. In the case of the MoS2 flakes with a BL, the vibrational modes of the Raman scattering did not shift. Conversely, the two Raman peaks of the MoS2 flake without BL red-shifted because of increasing electron-phonon scattering. The effect of area-selective doping was confirmed by electrical measurements. The field-effect mobility and the subthreshold swing were enhanced from 4.07 to 31.5 cm2/V·s and from 1.26 to 0.401 V/decade, respectively.