Optimization of surface passivation for suppressing leakage current in GaSb PIN devices

The suppression of leakage current via surface passivation plays a critical role for GaSb based optoelectronic devices. In this study, the sulfur passivation parameters are carefully optimized in this study for improving the performance of GaSb p-i-n devices. Two competing processes are evaluated during the sulfur passivation process: the hydrolysis and oxidation of HS�- ions that aide surface passivation and re-oxidation, respectively. Upon the optimization of sulfur passivation parameters and subsequent encapsulation with ALD Al2O3, the surface resistivity significantly increased from 4.3kΩ∙cm to 28.6kΩ∙cm, leading to 19.1 times drop in dark current at room temperature for the GaSb p-i-n structure. This work provides a repeatable and stable passivation approach for improving the optoelectronic performance of GaSb based devices

Bond-Selective Intensity Diffraction Tomography

Recovering molecular information remains a grand challenge in the widely used holographic and computational imaging technologies. To address this challenge, we developed a computational mid-infrared photothermal microscope, termed Bond-selective Intensity Diffraction Tomography (BS-IDT). Based on a low-cost brightfield microscope with an add-on pulsed light source, BS-IDT recovers both infrared spectra and bond-selective 3D refractive index maps from intensity-only measurements. High-fidelity infrared fingerprint spectra extraction is validated. Volumetric chemical imaging of biological cells is demonstrated at a speed of ~20 seconds per volume, with a lateral and axial resolution of ~350 nm and ~1.1 micron, respectively. BS-IDT's application potential is investigated by chemically quantifying lipids stored in cancer cells and volumetric chemical imaging on Caenorhabditis elegans with a large field of view (~100 micron X 100 micron)

UBE2C Is a Potential Biomarker of Intestinal-Type Gastric Cancer With Chromosomal Instability

This study explored potential biomarkers associated with Lauren classification of gastric cancer. We screened microarray datasets on gastric cancer with information of Lauren classification in gene expression omnibus (GEO) database, and compared differentially expressing genes between intestinal-type or diffuse-type gastric cancer. Four sets of microarray data (GSE2669, GSE2680, GDS3438, and GDS4007) were enrolled into analysis. By differential gene analysis, UBE2C, CDH1, CENPF, ERO1L, SCD, SOX9, CKS1B, SPP1, MMP11, and ANLN were identified as the top genes related to intestinal-type gastric cancer, and MGP, FXYD1, FAT4, SIPA1L2, MUC5AC, MMP15, RAB23, FBLN1, ANXA10, and ADH1B were genes related to diffuse-type gastric cancer. We comprehensively validated the biological functions of the intestinal-type gastric cancer related gene UBE2C and evaluated its clinical significance on 1,868 cases of gastric cancer tissues from multiple medical centers of Shanghai, China. The gain of copy number on 20q was found in 4 out of 5 intestinal-type cancer cell lines, and no similar copy number variation (CNV) was found in any diffuse-type cancer cell line. Interfering UBE2C expression inhibited cell proliferation, migration and invasion in vitro, and tumorigenesis in vivo. Knockdown of UBE2C resulted in G2/M blockage in intestinal-type gastric cancer cells. Overexpression of UBE2C activated ERK signal pathway and promoted cancer cell proliferation. U0126, an inhibitor of ERK signaling pathway reversed the oncogenic phenotypes caused by UBE2C. Moreover, overexpression of UBE2C was identified in human intestinal-type gastric cancer. Overexpression of UBE2C protein predicted poor clinical outcome. Taken together, we characterized a group of Lauren classification-associated biomarkers, and clarified biological functions of UBE2C, an intestinal-type gastric cancer associated gene. Overexpression of UBE2C resulted in chromosomal instability that disturbed cell cycle and led to poor prognosis of intestinal-type gastric cancer

Sub-surface imaging of porous GaN distributed Bragg reflectors via backscattered electrons

In this article, porous GaN distributed Bragg reflectors (DBRs) were fabricated by epitaxy of undoped/doped multilayers followed by electrochemical etching. We present backscattered electron scanning electron microscopy (BSE-SEM) for sub-surface plan-view imaging, enabling efficient, non-destructive pore morphology characterization. In mesoporous GaN DBRs, BSE-SEM images the same branching pores and Voronoi-like domains as scanning transmission electron microscopy. In microporous GaN DBRs, micrographs were dominated by first porous layer features (45 nm to 108 nm sub-surface) with diffuse second layer (153 nm to 216 nm sub-surface) contributions. The optimum primary electron landing energy (LE) for image contrast and spatial resolution in a Zeiss GeminiSEM 300 was approximately 20 keV. BSE-SEM detects porosity ca. 295 nm sub-surface in an overgrown porous GaN DBR, yielding low contrast that is still first porous layer dominated. Imaging through a ca. 190 nm GaN cap improves contrast. We derived image contrast, spatial resolution, and information depth expectations from semi-empirical expressions. These theoretical studies echo our experiments as image contrast and spatial resolution can improve with higher LE, plateauing towards 30 keV. BSE-SEM is predicted to be dominated by the uppermost porous layer's uppermost region, congruent with experimental analysis. Most pertinently, information depth increases with LE, as observed

Blind motion deblurring using improved DeblurGAN

Abstract To develop a fast and effective image deblurring method, the blind recovery of motion‐blurred images based on DeblurGAN(GAN, Generative Adversarial Networks) is researched.Firstly, the number of residual modules in the DeblurGAN network is changed, and an attempt is made to optimize the network structure to achieve better results in the blind recovery of motion‐blurred images. Secondly, an image deblurring method based on the improved DeblurGAN network is proposed.This paper makes corresponding adjustments to the generator and discriminator networks to change their input and output size to 512 × 512 while keeping the overall structure of the network unchanged, and the experimental results show that the quality of the restored images has been greatly improved. In addition, the images were divided into four classes of images,to achieve improved restoration of blurred images with specific content. Experimental results on the benchmark GoPro dataset validate that the improved DeblurGAN achieves more than 1.5 dB improvement than DeblurGAN in terms of peak signal‐to‐noise ratio (PSNR) as trained utilizing the same amount of data, and structural similarity assessment (SSIM) evaluation means and maximum values increased between 0.2 and 0.3. The improved DeblurGAN is more effective in terms of both blur removal and detail recovery

Multi-Labelled Classification Using Maximum Entropy Method

Many classification problems require classifiers to assign each single document into more than one category, which is called multilabelled classification. The categories in such problems usually are neither conditionally independent from each other nor mutually exclusive, therefore it is not trivial to directly employ state-of-theart classification algorithms without losing information of relation among categories. In this paper, we explore correlations among categories with maximum entropy method and derive a classification algorithm for multi-labelled documents. Our experiments show that this method significantly outperforms the combination of single label approach

Fast Band-Sweep Total Isotropic Sensitivity Measurement

To provide consistent measurements of radio performance in typical complex environments, the total isotropic sensitivity (TIS) is used as a key parameter measured in anechoic chambers. Currently, the TIS measurement is based on the integration of the measured effective isotropic sensitivity at every angle over a spherical surface. This measurement is time consuming so it is only performed for three channels in a band in order to reduce overall measurement time. However, the whole band performance in real environments is critical in the research and development stage, and even in potential certification measurement. A novel fast band-sweep measurement for TIS of wireless devices is proposed in this paper. This method measures the radiated sensitivity and the average gain of the receiver antenna separately, and then combines them to obtain the TIS. The measurement of the radiated sensitivity in a band is efficiently performed based on the relationship between the bit error rate and the received power, and the band-sweep average gain of mobile antennas can be achieved through peak gain measurements. Hence, this method reduces band-sweep measurement time significantly and also ensues the measurement accuracy by eliminating the systematic error in the received signal strength indicator reporting

Research data supporting "Microscopy studies of InGaN MQWs overgrown on porosified InGaN superlattice pseudo-substrates"

This dataset contains Energy-dispersive X-ray spectroscopy (EDX) data of multiple quantum wells (MQWs) overgrown on as-grown and porosified InGaN-based superlattice pseudo-substrates. Five pairs of nominally 7 nm-thick In0.06Ga0.94N quantum barriers (QBs) and 3 nm-thick In0.1Ga0.9N QWs were overgrown on two different templates that were etched under medium voltages (sample B2) and high voltages (sample B3) to achieve porosification. The edge of each sample wafer has intentionally remained un-etched as a non-porous comparator. Lamella of each sample have been prepared using standard lift-off procedures. Elemental mapping of the InGaN MQWs was carried out using EDX in a Thermo Fisher ScientificTM Spectra 300 scanning transmission electron microscope. From each lamella three different EDX profiles with a step size of 0.65 nm and integrated over a width of about 38 nm were collected. The regions for the EDX analysis were chosen so that they are at least 1 µm apart from each other and do not overlap with the sidewalls of V-pits and other structural inhomogeneities at which the local composition might vary due to differences in the incorporation efficiency. The data in this dataset are visualized in Figure 6 of the associated publication.We would like to thank Innovate UK for the financial support within the Collaborative Research and Development scheme “Porous InGaN for Red LEDs (PIRL)” (Ref. 107470) and the EPSRC for support through Cambridge Royce facilities grant EP/P024947/1 and Sir Henry Royce Institute - recurrent grant EP/R00661X/1. We acknowledge the use of the Thermo Fisher Spectra 300 TEM funded by EPSRC under grant EP/R008779/1. We acknowledge the support of the technical staff Wolfson Electron Microscopy Suite at the University of Cambridge. This work was also supported by the Royal Academy of Engineering under the Chair in Emerging Technologies programme funded by the Department of Science, Innovation and Technology (DSIT)