27,829 research outputs found
Intentionally Carbon-Doped AlGaN/GaN HEMTs:Necessity for Vertical Leakage Paths
No full textDynamic ON-resistance (RON) in heavily carbon doped AlGaN/GaN high electron mobility transistors is shown to be associated with the semi-insulating carbon-doped buffer region. Using transient substrate bias, differences in RON dispersion between transistors fabricated on nominally identical epilayer structures were found to be due to the band-to-band leakage resistance between the buffer and the 2DEG. Contrary to normal expectations, suppression of dynamic RON dispersion in these devices requires a high density of active defects to increase reverse leakage current through the depletion region allowing the floating weakly p-type buffer to remain in equilibrium with the 2DEG
AlN/GaN-based MOS-HEMT technology: processing and device results
No full textProcess development of AlN/GaN MOS-HEMTs is presented, along with issues and problems concerning the fabrication processes. The developed technology uses thermally grown Al<sub>2</sub>O<sub>3</sub> as a gate dielectric and surface passivation for devices. Significant improvement in device performance was observed using the following techniques: (1) Ohmic contact optimisation using Al wet etch prior to Ohmic metal deposition and (2) mesa sidewall passivation. DC and RF performance of the fabricated devices will be presented and discussed in this paper
Behavioral modeling of GaN-based power amplifiers: impact of electrothermal feedback on the model accuracy and identification
No full textIn this article, we discuss the accuracy of behavioral models in simulating the intermodulation distortion (IMD) of microwave GaN-based high-power amplifiers in the presence of strong electrothermal (ET) feedback. Exploiting an accurate self-consistent ET model derived from measurements and thermal finite-element method simulations, we show that behavioral models are able to yield accurate results, provided that the model identification is carried out with signals with wide bandwidth and large dynamics
Chao leng xuan liang hun he wu zhong de yi he jian xiang gan zi xuan dong li xue
No full textLi, Xiaoke = 超冷旋量混合物中的異核間相干自旋動力學 / 李小科.Thesis Ph.D. Chinese University of Hong Kong 2015.Includes bibliographical references (leaves 126-142).Abstracts also in Chinese.Title from PDF title page (viewed on 25, October, 2016).Li, Xiaoke = Chao leng xuan liang hun he wu zhong de yi he jian xiang gan zi xuan dong li xue / Li Xiaoke
Study on surface morphology of GaN growth by MOCVD on GaN/Si(111) template
No full textThe surface morphology of GaN grown by MOCVD on GaN/Si template was studied. Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied. The formation of rough morphology is possibly related to Ga-Si alloy produced due to poor thermal stability of template at high temperature. The deep pinhole defects generated are deep down to the surface of MBE-grown GaN/Si template. The stress originated from the large thermal expansion coefficient difference between GaN and Si may be related to the formation of the pinhole defects. The surface morphology of the GaN can be improved by optimizing the GaN/Si template and decreasing the growth temperature
LCT-GAN - Improving the efficiency of tabular data synthesis via latent embeddings
No full textIn the past decade data-driven approaches have been at the core of many business and research models. In critical domains such as healthcare and banking, data privacy issues are very stringent. Synthetic tabular data is an emerging solution to privacy guarantee concerns. Generative Adversarial Networks (GANs) are one of the emerging solutions for synthesizing data. However in order to capture all relevant relationships between columns, tabular data needs to be numerically encoded. As columns might be of different types, this is a challenging task as proven by recent approaches. Throughout this paper, we focus on the dimensionality explosion problem, which leads to high-dimensional datasets alongside computational overhead and increase in training time. We introduce a novel synthesis pipeline - LCT-GAN - an improvement to the current state-of-the-art in tabular data synthesis CTAB-GAN. Our approach addresses the dimensionality explosion problem by introducing a low-dimensional embedding step via an autoencoder prior to training. It is then combined with a novel conditional GAN architecture, operating in latent space. After thorough evaluation, we observe that our solution achieves more than 30\% improvement in certain statistical metrics in comparsion to CTAB-GAN, accompanied by 5 fold decrease in size and 150 times speedup in training time for a single epoch. We successfully show that it is possible to embed data using autoencoders, and that GANs are able to learn complex relationships in latent space in the context of tabular data.CSE3000 Research ProjectComputer Science and Engineerin
0.35 MICROMETER EEPROM SHRINK CELL QUALIFICATION
No full textMaster'sMASTER OF SCIENCE IN ADVANCED MATERIALS FOR MICRO- & NANO- SYSTEMSDissertation Supervisors: 1. Assistant Professor Gan Chee Lip, NTU. 2. Mr.Li Weining, Chartered. 3. Mr. Li Zhaobing, Chartere
Improvement of the efficiency droop of GaN-LEDs using an AlGaN/GaN superlattice insertion layer
No full textWith an n-AlGaN(4 nm)/GaN(4 nm) superlattice(SL) inserted between an n-GaN and an InGaN/GaN multiquantum well active layer, the efficiency droop of GaN-based LEDs has been improved. When the injection current is lower than100 mA, the lumen efficiency of the LED with an n-AlGaN/GaN SL is relatively small compared to that without an n-AlGaN/GaN SL. However, as the injection current increases more than100 mA, the lumen efficiency of the LED with an n-AlGaN/GaN SL surpasses that of an LED without an n-AlGaN/GaN SL. The wall plug efficiency of an LED has the same trend as lumen efficiency. The improvement of the efficiency droop of LEDs with n-AlGaN/GaN SLs can be attributed to a decrease in electron leakage due to the enhanced current spreading ability and electron blocking effect at high current densities. The reverse current of LEDs at-5 V reverse voltage decreases from0.2568029 to0.0070543μA, and the electro-static discharge(ESD) pass yield of an LED at human body mode(HBM)-ESD impulses of2000 V increases from60% to90%.?2011 Chinese Institute of Electronics
Duo dian xie zuo: gan rao jian qing yu gan rao li yong
No full textShen, Siduo.Thesis Ph.D. Chinese University of Hong Kong 2014.Includes bibliographical references (leaves 147-161).Abstracts also in Chinese.Title from PDF title page (viewed on 15 September, 2016).Shen, Siduo = Duo dian xie zuo : gan rao jian qing yu gan rao li yong / Shen, Siduo
Polarity Control of GaN and Realization of GaN Schottky Barrier Diode Based on Lateral Polarity Structure
No full textThis paper reports investigation on a polarity control scheme of GaN thin films and realization of Schottky barrier diode (SBD) fabricated on a lateral-polarity-structure (LPS) GaN without intentionally doping. Specifically, Ga-polar and N-polar GaN were grown simultaneously side by side on sapphire substrate with patterned AlN buffer. Due to the surface energy difference between two polarities, N-polar regions are n-type conductive with rough surfacemorphology, whileGa-polar regions are semiinsulating with atomic flat surface morphology. Annealing conditions of both ohmic contactand Schottky contactwere investigated. Current-voltage (I-V) characteristic revealed that the SBD fabricated on LPS GaN has higher forward current, barrier height closer to 0.7 eV, and ideality factor closer to unity compared to SBD fabricated on conventional undopedGaN. The specific on-state resistance (R-ON) for the SBD based on LPS GaN is 77 m Omega . cm(2) lower than the SBD fabricated on conventional GaN. With oxide passivation on SBD surface, forward current exceeds 0.2 A at 10 V, while reverse current is less than 10(-5) A at -10 V, respectively. The utilization of LPS in SBD demonstrates a promising approach for the development of lateral n(+)/n(-) SBD with a simple fabrication scheme
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