RESUMEN
The metal-semiconductor (M-S) contact is usually an Ohmic contact or a Schottky contact, which greatly affects the electronic properties of devices, and it remains a huge challenge to realize a low-resistance Ohmic contact in a metal-semiconductor junction (MSJ). Herein, we systematically studied the band structures, electrostatic potential, charge transfer, Schottky barrier height of carriers, effective carrier masses, and tunneling probability of carriers of a germanene (Ge)/GaAs MSJ. The transition from the Schottky to the Ohmic contact can be caused by applying certain biaxial strains or electric fields, which weakens the Fermi level pinning (FLP) effect and reduces contact resistance. Meanwhile, the electron injection efficiency of Ge/(GaAs)As MSJ (PTB > 27%) is far superior to that of other two-dimensional (2D) vdW MSJs. This work indicates that Ge/GaAs heterostructures are the most compatible for applying high-effective 2D electronic nanodevices under controllable conditions.
RESUMEN
Recently, the energy crisis and environmental pollution problems have become increasingly severe. There is an urgent need to develop a class of multifunctional materials that can both produce clean energy and detect harmful gases. Herein, we propose a g-GaN/SnS heterostructure and explored its dual-optimal performance in photocatalytic hydrogen production and gas detection. Our results demonstrated that the g-GaN/SnS heterostructure has a suitable type II band alignment and excellent absorption in the visible range, which both indicate its potential application in photocatalysis. Furthermore, when the g-GaN/SnS heterostructure acted as a gas detection material, it was consistently susceptible to NO2 gas molecules, according to charge transfer. Additionally, it has a very suitable material recovery time (â¼0.5 h) when used for NO2 detection, illustrating the recyclability of the material. Interestingly, the applied electric field of -0.4 V/Å can greatly increase the absorption coefficient in the visible range to 150% of the original. Also, the applied electric field of 0.6 V/Å can substantially enhance the gas detection sensitivity by 27% compared to the case without the electric field. Thus, the g-GaN/SnS heterostructure we proposed not only has the advantage of being bifunctional but also has the potential to be recycled.
RESUMEN
With the increasing environmental pollution and energy crisis, it is significant to develop environmentally friendly and adjustable photocatalysts for water splitting. Here we explored the optoelectronic properties of several H-GaN/MgI2 vdW heterostructures by regulating different polarization surfaces and numbers of GaN layers. Our results demonstrate that all structures, except 2L-Ga-GaN/MgI2, exhibit excellent physical stability. Moreover, the band structures and band edge positions demonstrate that only the heterostructure of 3L-Ga-GaN/MgI2 with both suitable band alignment (type-II) and an acceptable band gap (â¼1.92 eV) is most satisfactory for water splitting. Additionally, the absorption coefficient of the 3L-Ga-GaN/MgI2 heterostructure can reach over â¼105 cm-1, which has further confirmed its excellent advantage in photocatalysis. Finally, in the case of 6% external strain for the 3L-Ga-GaN/MgI2 heterostructure, a rollover in band alignment (from type-II to type-I) is exhibited. These promising features of the GaN/MgI2 vdW heterostructure give a new paradigm for developing novel efficient and adjustable photocatalytic water-splitting materials.
RESUMEN
Near-infrared InxGa1-xAs photocathode with better optoelectronic properties is a good candidate for low-light-level (LLL) night-vision system. However, the residual gases in the ultra-high vacuum (UHV) system inevitably affects the stability and photo-emission performance of LLL photoelectric devices such as their quantum efficiency and life-time. In this study, the first-principles calculations were used to investigate the adsorption effect of five different residual gas species, including H2, CH4, CO, H2O and CO2 on Cs-sensitized In0.53Ga0.47As (001) ß2 (2 × 4) surface. The study results indicate that CO2 gas molecule is the most easily attached to the Cs-sensitized surface. The adsorption of residual gases leads to the formation of a new dipole pointing from inner Cs atoms to gas molecules. It makes the charge center of the adsorbates escape from the surface, which weakens the interaction between the inner Cs atoms and the clean surface. This results in the increase of the surface work function and degradation of the performance of photoelectric devices. Also, the adsorption of residual gas molecules influences the absorption and reflection coefficients of Cs-sensitized In0.53Ga0.47As (001) ß2 (2 × 4) surface.
