Methylammonium lead halide perovskites have attracted enormous attentions due to their superior optical and electronic properties. However, the photodetection at near-infrared telecommunication wavelengths is hardly achievable because of their wide bandgaps. Here, this study demonstrates, for the first time, novel perovskite-erbium silicate nanosheet hybrid photodetectors with remarkable spectral response at ≈1.54 µm. Under the near-infrared light illumination, the erbium silicate nanosheets can give strong upconversion luminescence, which will be well confined in their cavities and then be efficiently coupled into and simultaneously excite the adjacent perovskite to realize photodetection. These devices own prominent responsivity and external quantum efficiency as high as previously reported microscale silicon-based subbandgap photodetectors. More importantly, the photoresponse speed (≈900 µs) is faster by five orders than the ever reported hot electron silicon-based photodetectors at telecommunication wavelengths. The realization of perovskite-based telecommunication band photodetectors will open new chances for applications in advanced integrated photonics devices and systems.
van der Waals (vdW) vertical p−n junctions based on two-dimensional (2D) materials have shown great potential in flexible, self-driven, high-efficiency electronic and optoelectronic applications. However, due to the complex nucleation dynamics, the controllable synthesis of vertical heterostructures remains a daunting challenge. Here, we report the controlled growth of vertical GaSe/MoS 2 p−n heterojunctions via a liquid gallium (Ga)-assisted chemical vapor deposition method. The growth mechanism can be interpreted by theoretical calculations based on the Burton−Cabrera− Frank theory. By analyzing the diffusion barriers and the Ehrlich−Schwoebel barriers of adatoms, we found that the growth modes between vertical and lateral can be precisely switched by means of adjusting the amount of Ga. Based on the achieved high-quality vertical GaSe/MoS 2 p−n heterojunctions, photosensing devices are further designed and systematically investigated. Upon light illumination, prominent photovoltaic effects with large open-circuit voltage (0.61 V) and broadband detection capability from 375 to 633 nm are observed, which can further be employed for self-powered photodetection with high responsivity (900 mA/W) and fast response speed (5 ms). The developed liquid-metal-assisted strategy provides an effective method for controllable synthesis of vdW heterostructures and will give impetus to their applications in highperformance optoelectronic device.
Misfit defects in a 3C-SiC/Si (001) interface were investigated using a 200 kV high-resolution electron microscope with a point resolution of 0.194 nm. The [110] high-resolution electron microscopic images that do not directly reflect the crystal structure were transformed into the structure map through image deconvolution. Based on this analysis, four types of misfit dislocations at the 3C-SiC/Si (001) interface were determined. In turn, the strain relaxation mechanism was clarified through the generation of grow-in perfect misfit dislocations (including 90° Lomer dislocations and 60° shuffle dislocations) and 90° partial dislocations associated with stacking faults.
Novel β-In2Se3/MoS2 vertically stacked heterostructures were synthesized, and can be further utilized as excellent photodetectors in the visible and near-infrared range.
We investigate the origin of yellow luminescence in n-type GaN. It is found that the relative intensity of yellow luminescence increases as the full width at half maximum of the x-ray diffraction rocking curve at the (102) plane increases. This indicates that the yellow luminescence is related to the edge dislocation density. In addition, the relative intensity of yellow luminescence is confirmed to increase with increasing Si doping for the high quality GaN we have obtained. We propose that the yellow luminescence is effectively enhanced by the transition from donor impurities such as Si to acceptors around the edge dislocations in n-type GaN.
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