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2022 ◽  
Vol 43 (1) ◽  
pp. 012303
Author(s):  
Xiujun Hao ◽  
Yan Teng ◽  
He Zhu ◽  
Jiafeng Liu ◽  
Hong Zhu ◽  
...  

Abstract We demonstrate a high-operating-temperature (HOT) mid-wavelength InAs/GaSb superlattice heterojunction infrared photodetector grown by metal–organic chemical vapor deposition. High crystalline quality and the near-zero lattice mismatch of a InAs/GaSb superlattice on an InAs substrate were evidenced by high-resolution X-ray diffraction. At a bias voltage of –0.1 V and an operating temperature of 200 K, the device exhibited a 50% cutoff wavelength of ~ 4.9 μm, a dark current density of 0.012 A/cm2, and a peak specific detectivity of 2.3 × 109 cm·Hz1/2 /W.


Author(s):  
P. Gayathri

Abstract: Imidazolium hydrogen squarate (IHS) crystal has been grown by slow evaporation solution growth technique at room temperature. The lattice parameters of grown crystal were determined using single crystal X-ray diffraction data and compared with powder XRD. Single crystal XRD shows that the crystal crystallizes in monoclinic system with noncentrosymmetric space group Pc. The crystallinity of the grown crystal was confirmed by X-ray powder diffraction analysis. FT-IR and FT-RAMAN analyses qualitatively confirm the various functional groups present in the grown crystal. The 1H and 13C NMR spectra were recorded to establish the molecular structure. Thermal properties of title crystal were studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The UV-Vis-NIR transmission spectrum was recorded to find the band width of optical transmittance window and the lower cutoff wavelength. The optical band gap value of the material is evaluated to be 5.6 eV. The second harmonic generation efficiency was calculated by the Kurtz and Perry powder method using a Q-switched mode locked Nd: YAG laser emitting 1064 nm laser as source. Finally, Z-scan technique was employed to determine the nonlinear refractive index, nonlinear absorption coefficient and third-order NLO susceptibility to find suitability of the grown crystal in photonics and optoelectronics applications. Keywords: Single crystal; Powder XRD; thermal analysis; SHG; Z-scan studies


Photonics ◽  
2021 ◽  
Vol 8 (12) ◽  
pp. 564
Author(s):  
He Zhu ◽  
Jiafeng Liu ◽  
Hong Zhu ◽  
Yunlong Huai ◽  
Meng Li ◽  
...  

High operating temperature mid-wavelength InAs/GaSb superlattice infrared photodetectors with a single heterojunction structure grown by metal–organic chemical vapor deposition are reported. By inserting a fully-depleted wider-gap barrier layer between the absorber and the p-contact, “diffusion-limited” behavior has been achieved for the heterojunction “PNn” device, in contrast to the conventional pin homojunction device. The PNn device with a 50% cutoff wavelength of 4.5 μm exhibited a dark current of 2.05 × 10−4 A/cm2 and a peak specific detectivity of 1.28 × 1011 cm·Hz·W−1 at 150 K and a reverse bias of −0.1 V.


2021 ◽  
Vol 9 (2) ◽  
pp. 46-50
Author(s):  
Muhanad A. Ahmed ◽  
Mohammed F. Mohammed Sabri ◽  
Wathiq R. Abed

In this paper, nanostructured silicon carbide (SiC) thin films are deposited onto glass substrate using pulsed laser deposition technique. Electrical and optical characterizations such as conductivity, resistivity, transmission, Seeback effect, absorption, absorption coefficient, energy band gap, and extinction coefficient as a function of photon energy, and the effect of thin films thickness on transmission are carried out to characterize the prepared samples. Results showed that the prepared SiC thin film is an n-type semiconductor with an indirect bandgap of ~3 eV, 448 nm cutoff wavelength, 3.4395 × 104 cm−1 absorption coefficient and 0.154 extinction coefficient. The surface morphology of the SiC thin films is studied using scanning electron microscope at a substrate temperature of 400 °C and it is found that the grain size of the prepared SiC thin film is about 30 nm. As such, the nano thin films optical and structural characteristics enable the films to be used as gases sensors in many optoelectronic devices such as the environment and ultraviolet photodiode.


2021 ◽  
Vol 922 (1) ◽  
pp. 10
Author(s):  
Kedron Silsbee ◽  
Alexei V. Ivlev ◽  
Munan Gong

Abstract We present a generic mechanism for the thermal damping of compressive waves in the interstellar medium (ISM), occurring due to radiative cooling. We solve for the dispersion relation of magnetosonic waves in a two-fluid (ion-neutral) system in which density- and temperature-dependent heating and cooling mechanisms are present. We use this dispersion relation, in addition to an analytic approximation for the nonlinear turbulent cascade, to model dissipation of weak magnetosonic turbulence. We show that in some ISM conditions, the cutoff wavelength for magnetosonic turbulence becomes tens to hundreds of times larger when the thermal damping is added to the regular ion-neutral damping. We also run numerical simulations, which confirm that this effect has a dramatic impact on cascade of compressive wave modes.


Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2807
Author(s):  
Yangan Zhang ◽  
Yao Li ◽  
Xueguang Yuan ◽  
Xin Yan ◽  
Xia Zhang

A laterally oriented GaAs p-i-n nanowire solar cell with Ag gratings is proposed and studied via coupled three-dimensional optoelectronic simulations. The results show that the gratings significantly enhance the absorption of nanowire for both TM and TE polarized light due to the combined effect of grating diffraction, excitation of plasmon polaritons, and suppression of carrier recombination. At an optimal grating period, the absorption at 650–800 nm, which is an absorption trough for pure nanowire, is substantially enhanced, raising the conversion efficiency from 8.7% to 14.7%. Moreover, the gratings enhance the weak absorption at long wavelengths and extend the absorption cutoff wavelength for ultrathin nanowires, yielding a remarkable efficiency of 13.3% for the NW with a small diameter of 90 nm, 2.6 times that without gratings. This work may pave the way toward the development of ultrathin high-efficiency nanoscale solar cells.


Crystals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1239
Author(s):  
C. Rathika Thaya Kumari ◽  
Ahmed Al Otaibi ◽  
T. Kamaraj ◽  
M. Nageshwari ◽  
G. Mathubala ◽  
...  

Urea glutaric acid (UGA), an organic crystal, was synthesized and grown using a low temperature solution technique. Single crystal XRD revealed a monoclinic structure with a C2/C space group. The various cell data were identified. The optical parameters were calculated from UV-visible spectrum. The transmittance spectra showed the cutoff wavelength as 240 nm (low) and the energy gap determined from the spectra was compared with the theoretical energy gap. The transition number revealed the electron transition, which corresponded to direct allowed transition. The diverse optical parameters like reflectance, extinction coefficient, refractive index and optical susceptibility were determined. The least value of Urbach energy caused less defects and a good crystalline nature. The steepness value and electron phonon interaction were calculated. The positions of lower and higher band energy levels were identified. Electronic polarizability was found using the Clausius–Mossoti relation and tabulated. The mechanical fitness was measured from Vickers hardness analysis. The nonlinear optical property was measured from Z-scan analysis. Thus, the optical results support the material suitability and fitness for optical and electronic domain applications.


2021 ◽  
pp. 17-25
Author(s):  
Anatoly Sviridov ◽  
Leonid Saginov

The paper proposes a new method for calculating the integral and spectral radiation coeffi-cients of extended subwavelength particles (ESPs), which include micro and nanocylinders and parallelepipeds. Comparison of the results of calculations by the proposed method with the calculated and experimental data found in the literature is carried out. It is shown that with decrease in only the transverse dimensions of the ESP (from values much larger than λmax to values much smaller than max) from the radiation spectrum, which was originally de-scribed by Planck's law and contained modes with both polarization directed along the axis and with polarization directed perpendicular to the axis , modes with wavelengths exceeding λcutoff (λcutoff is the cutoff wavelength) and having polarization perpendicular to the longi-tudinal axis of the ESP will be gradually eliminated, while modes with wavelengths polarized along the ESP axis will always be present in the radiation spectrum of the ESP. When the transverse dimensions of the ESP become much less than λmax, then all modes with polariza-tion perpendicular to the axis will disappear from the emission spectrum of this ESP, and on-ly modes with longitudinal polarization will remain. This is a fundamental difference from the SPs considered earlier in [16, 17], where methods for calculating SPs as disks, spheres, cubes were proposed. All the proposed calculation methods use the formalism of the decom-position of radiation fluxes into spectral-spatial modes.


Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1058
Author(s):  
Juan M. González-Leal ◽  
Enrique Gallero ◽  
Eduardo Blanco ◽  
Milagrosa Ramírez del Solar ◽  
Andrés Nuñez ◽  
...  

This article reports on the relation between the surface topography and the optical reflectance, both total and diffuse, of different samples of AISI 430 ferritic stainless steel. Gaussian filters with different cutoff wavelengths were applied to the height maps of the surface topography of the samples, to separate the different scales of surface roughness involved in optical scattering in the visible range of the spectrum. Significant anisotropy, related to the rolling process, was found in the topography. An effective roughness slope parameter was defined from the dependence of the ratio between the root mean square height and the autocorrelation length on the cutoff wavelength. This roughness slope demonstrated an exceptionally good linear relationship with CIE 1931 luminance, which was calculated from the diffuse reflection spectra. The color uniformity of the samples was analyzed based on their CIE L*a*b* coordinates under daylight and LED illumination. The results confirmed the strong influence of manufacturing process on the surface characteristics of AISI 430 ferritic stainless steel sheet products with a bright finish.


2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Ju Sun ◽  
Nong Li ◽  
Qing-Xuan Jia ◽  
Xuan Zhang ◽  
Dong-Wei Jiang ◽  
...  

AbstractThe InAs/GaSb superlattice infrared detector has been developed with tremendous effort. However, the performance of it, especially long-wavelength infrared detectors (LWIR), is still limited by the electrical performance and optical quantum efficiency (QE). Forcing the active region to be p-type through proper doping can highly improve QE, and the gating technique can be employed to greatly enhance electrical performance. However, the saturation bias voltage is too high. Reducing the saturation bias voltage has broad prospects for the future application of gate voltage control devices. In this paper, we report that the gated P+–π–M–N+ InAs/GaSb superlattice long-wavelength infrared detectors exhibit different π region doping levels that have a reduced minimum saturation bias at − 10 V with a 200-nm SiO2 layer after a simple and effective anodic vulcanization pretreatment. The saturation gate bias voltage is much lower than − 40 V that reported with the same thickness of a 200-nm SiO2 passivation layer and similar structure. The optical and electrical characterization indicates that the electrical and optical performance of the device would be weakened by excessive doping concentration. At 77 K, the 50% cutoff wavelength of the device is about 8 µm, the 100% cutoff wavelength is 10 µm, the maximum quantum efficiency is 62.4%, the maximum of responsivity is 2.26 A/W at 5 µm, and the maximum RA of the device is 1259.4 Ω cm2. Besides, the specific detectivity of Be 780 °C-doped detector without gate electrode exhibits a peak of 5.6 × 1010 cm Hz1/2/W at 5 µm with a 70-mv reverse bias voltage, which is more than three times that of Be 820 °C-doped detector. Moreover, the peak specific detectivity could be further increased to 1.3 × 1011 cm Hz1/2/W at 5 µm with a 10-mv reserve bias voltage that has the bias of − 10 V at the gate electrode.


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