Transition metal dichalcogenides (TMDs) are widely utilized in spintronic and optoelectronic technologies due to their two-dimensional nature. In recent times, there has been a notable surge of interest in transition-metal disulfides, specifically molybdenum disulfide (MoS2) and tungsten disulfide (WS2), as exceptional materials for investigating fundamental physics in the realm of two-dimensional materials. The synthesis of MoxW(1−x)S2 alloys through experimental techniques has played a pivotal role in harnessing the unique properties of both MoS2 and WS2. Notably, trilayer TMDs exhibit properties such as tunable bandgap, higher exciton binding energy, and interlayer interaction, all of which contribute to the emergence of novel optical phenomena, including new optical modes and excitonic resonances. In this study, we investigate the potential of trilayer MoxW(1−x)S2 alloys using first-principle computational techniques. The analysis showed an indirect bandgap that ranged from approximately 1.34 to 1.39eV as the composition of the alloy varied from 74% Mo to 33% Mo. This tunability of the bandgap allows for precise control over the energy levels at which electronic transitions occur, enabling the material to adapt to specific device requirements. With an increasing percentage of tungsten (W) in the alloy, there was a pronounced peak shift in the out-of-plane absorption spectrum. The peak wavelength shifted from 1.95eV to 1.70eV, indicating that the material’s absorption properties could be tailored by adjusting the alloy composition. These findings open up possibilities for designing TMD-based photodetectors capable of detecting a wide range of light wavelengths.
Transition metal dichalcogenides are being used extensively due to their 2-D nature, in spintronic and optoelectronic technologies. TMDs, specifically molybdenum disulfide (MoS2) and tungsten disulfide (WS2), have recently attracted considerable interest and extensive research has been dedicated to these materials, unveiling their immense potential for various applications such as catalysts, lubricants, lithium batteries, phototransistors, and nanoelectronics. MoxW1−xS2 alloys have been synthesized via experimental techniques to harness the properties of both materials. Bilayer TMDs exhibit properties such as tunable bandgap, higher exciton binding energy and interlayer interaction giving rise to new optical modes and excitonic resonances. In this work we study the utility of bilayer MoxW1−xS2 alloys through first principle computational techniques. We observe an indirect bandgap of around 1.49-1.55eV as we vary the composition of the alloy from 72% Mo to 22% Mo. This capability is significant as it allows researchers to precisely engineer the electronic and optical properties of the material to suit various device requirements. The out-of-plane absorption coefficient of the alloys shows a peak shift from 1.95eV to 2.55eV on increasing percentage of W in the alloy. This shift in the absorption spectrum indicates that the material can effectively absorb light of different wavelengths, thus enabling the design of TMD-based photodetectors with the capability to detect a broad range of wavelengths. This versatility in light absorption is of great importance for applications such as sensors, photovoltaics, optoelectronic devices, where the detection of specific wavelengths is crucial.
The formation of reproducible p-type conductivity in ZnO thin films is highly challenging now a days for the fabrication of several homo/heterojunction based fully transparent opto-electronic devices. In this study, p-type P: ZnO thin films are deposited by cost-effective SOD process and then intrinsically n-type Ga2O3 films are deposited on it to validate the p-type conductivity of ZnO by making vertical heterojunction with n-Ga2O3. The ZnO thin films are deposited by RF sputtering and subsequent P-doping is done by using the SOD technique on it. This involves proximity diffusing dopants into a spin-coated film by stacking the dopant source during thermal annealing at 800◦C for four hours in the furnace. Ga2O3 films are deposited on the P: ZnO films by using RF sputtering technique, for making the heterojunction. The electrical measurements are performed by using current-voltage (I-V) measurements under illuminated and dark conditions. The photo-switching and responsivity are also measured on the fabricated device. It is observed that the P: ZnO/Ga2O3 heterojunction exhibits the photoresponse in the dual wavelength region. The corresponding two peaks of responsivity are found around 200 nm and 390 nm with the values of 68.03 A/W and 7.93 A/W (at 5 V), respectively. Such two peaks originated due to the ultra-wide bandgaps of Ga2O3 (4.7eV) and P: ZnO (3.1 eV). Also, such heterojunction shows a rapid switching speed under white light at 5 V (rise time: 230 ms, fall time: 163 ms) and −5 V (rise time: 83 ms, Fall time: 169 ms), which is comparable with the other reported results. Therefore, the current study demonstrates the development of highly stable and reproducible p-type P: ZnO thin films by employing SOD technique and the validation of p-type formation by fabricating P: ZnO/Ga2O3 heterojunctions for dual-wavelength selector UV detector application and such detectors can be a potential candidate for various optoelectronic devices.
The potential utility of two-dimensional transition-metal dichalcogenides (TMDs) in electronics, thermoelectrics, and spintronics have sparked an increase in scientific interest in the same. In accordance with this, we have done a study on VS2 based device, using first principle Density Functional Theory (DFT) calculations combined with Non-equilibrium Green’s Function (NEGF) formalism to investigate spin transport properties. We constructed a toy-model of a 2-terminal VS2 based device using MATLAB, and further applied a tunneling potential barrier across the channel and measured current through the same, on applying voltage across the terminals. Using the data obtained, we analyzed the spin filtering effect in the device by considering spin splitting in presence of magnetic field, and plotting the spin polarization (SP) and the magnetoresistance (MR) against bias voltage, respectively. The SP is observed to be 36% for a ballistic device between a bias range of 0.3 and 0.5V, which increases to 63% on applying a potential barrier of height twice the Fermi level of VS2. For a ballistic device, we observed an increase in MR from 60% to 76% for large barrier height, within the same bias range as earlier. In each case, the peak value of current per unit cross sectional area of the device was found to be of the order of 10A/μm2. Using these findings, we can conclude that our modeled VS2 device exhibits properties to be used as a promising candidate for spintronic applications.
A comparative study of Stranski-Krastanov (SK), sub-monolayer (SML) and coupled SK on SML InAs quantum dots as active region in InGaAs/GaAs/AlGaAs DDWELL heterostructure was done. Incorporation of additional high band gap confinement enhancing (CE) AlxGa1-xAs barrier helps to create new energy levels, increase the absorption coefficient, reduce dark current and improve crystalline quality of the heterostructure. This is because of the CE barrier which reduces In-adatom out-diffusion. Three different DDWELL heterostructure A, B and C with active regions as SK, SML and SK on SML respectively, had been modelled using the Nextnano simulation tool keeping all other parameters same. Photoluminescence (PL) emission wavelength, biaxial strains and hydrostatic strain profiles of heterostructures A, B and C were compared. Hydrostatic strain with less magnitude leads to better carrier confinement within the conduction band, and biaxial strain with high magnitude increases splitting between heavy-hole and light- hole bands, generating a red-shift in PL emission wavelength. It can be observed from the computed result that biaxial and hydrostatic strain in the SK QD are enhanced in structure C compared to A. Likewise, biaxial strain and hydrostatic strain in the SML QD stacks are enhanced in structure C compared to B. PL emission wavelength of structures A, B, and C were observed to be 1116nm, 864nm and 1170nm respectively. Therefore, structure C exhibits minimum strain among the heterostructures and highest PL emission wavelength for SWIR applications.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.