Yunfei Hou

Hexi University

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Chunming Qiao

University at Buffalo, State University of New York

Yinxi Jin

Harbin Institute of Technology

Albert Chin

National Yang Ming Chiao Tung University

Adel W. Sadek

University at Buffalo, State University of New York

Dim‐Lee Kwong

Agency for Science, Technology and Research

Fan-Yu Yen

National Tsing Hua University

S.C. Chen

Taiwan Semiconductor Manufacturing Company (Taiwan)

H.J. Tao

Xiangtan University

K.F. Hulme

University at Buffalo, State University of New York

Chunxiang Zhu

National University of Singapore

Cooperative Institutions

Taiwan Semiconductor Manufacturing Company (Taiwan)

National University of Singapore

National Yang Ming Chiao Tung University

California State University, San Bernardino

Taiwan Semiconductor Manufacturing Company (United States)

University at Buffalo, State University of New York

Chinese Academy of Sciences

Institute of Microelectronics

Taiwan Semiconductor Manufacturing Company (China)

Agency for Science, Technology and Research

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Advanced Dual Metal Gate MOSFETs with High-k Dielectric for CMOS Application

P.F. Hsu Jian-Yuan Chiou Kai Yin Jae‐Joon Lee R.L. Hwang

This paper reports the fabrication of MOSFETs with dual metal gate electrodes. Low threshold voltage (Vt) was achieved using TaC for nFETs and MoNx for pFETs. The transistors show excellent Ion-Ioff performance with well-controlled short channel effects. Benefited from a novel approach in base oxide formation, high mobility at ~90% of poly/SiO ₂ was achieved on thick HfO ₂ (30A). Improvement in current drivability by the incorporation of conventional cap stressor was also presented. The data demonstrates one of the best MOSFETs to date with dual metal gates on high-k dielectrics. It is further observed that high-k crystallization induces Vt non-uniformity in small devices. To our knowledge, the impact of crystallization to high- k manufacturability is addressed here for the first time

Metal gate

High-κ dielectric

10.1109/vlsit.2006.1705192

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Citations (16)

Collusion prevention mechanism in PPP highway projects: Optimal government subsidy, toll and penalty

Economics of Transportation (2025)

Yunfei Hou Hongwei Wang Guanqun Shi

10.1016/j.ecotra.2025.100399

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Citations (0)

Effective Work Function Engineering of $\hbox{Ta}_{x}\hbox{C}_{y}$ Metal Gate on Hf-Based Dielectrics

IEEE Electron Device Letters (2007)

Fan-Yu Yen C.L. Hung Yunfei Hou P.F. Hsu Vincent S. Chang

This letter reports the engineering of effective work function (EWF) for tantalum carbide (TaC) metal gate on high-$k$ gate dielectrics. The dependence of EWF on Si concentration in HfSiO as well as nitridation techniques is revealed. The EWF was extracted by both terraced oxide and terraced high-$k$ techniques with the bulk and interface charges taken into account. The incorporation of Si in Hf-based dielectrics results in an increase of EWF, while the presence of N tends to decrease the EWF. Plasma nitridation is found to be more effective in lowering the EWF than a thermal nitridation. The phenomena can be explained by the modification of TaC/high-$k$ interface dipole moment, which arises from the electronegativity difference for various interface bonds. Based on the above findings, we proposed a novel approach to reduce the EWF of TaC on HfSiON by using a thin $\hbox{HfO}_{2}$ cap layer after optimizing the nitridation. The MOSFET results show that this technique is able to achieve a lower $V_{t}$ without degrading the device performance.

Metal gate

Electronegativity

10.1109/led.2007.891271

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Citations (3)

Towards efficient vacant taxis Cruising Guidance

2015 IEEE Global Communications Conference (GLOBECOM) (2013)

Yunfei Hou X. Li Yuanjie Zhao Xiaolin Jia Adel W. Sadek

Different from the conventional operation mode in existing taxi dispatch systems, in this paper, we envision a new cyber-technology enabled taxi dispatch system which can efficiently provide vacant taxis with cruising route suggestions, not to respond to any specific pick-up request but instead, hoping to find prospective customers (such system is also complementary to the conventional operation mode). We address the Taxi Cruising Guidance (TCG) problem with the objective being to minimize the Global Vacant Rate (GVR), which is defined as the ratio of traveling miles with no passenger onboard, to the total traveling miles in a given time period. We propose a number of heuristic solutions and conduct comprehensive performance evaluations based on large-scale simulations. A case study is also presented by utilizing real traces collected from taxis in the city of Shanghai. As part of our research, we leverage a well-known microscopic traffic simulator (called TRANSIMS) to demonstrate that the application of TCG is also beneficial to traffic management.

Taxis

Leverage (statistics)

Mode (computer interface)

10.1109/glocom.2013.6831047

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Citations (16)

Robust High-Quality HfN–>tex<$hbox HfO_2$>/tex<Gate Stack for Advanced MOS Device Applications

IEEE Electron Device Letters (2004)

H.Y. Yu Jinfeng Kang Chunyu Ren J.D. Chen Yunfei Hou

In this letter, a thermally stable and high-quality HfN-HfO/sub 2/ gate stack for advanced MOS applications is reported for the first time. Negligible changes in both equivalent oxide thickness (EOT) and work function of HfN-HfO/sub 2/ gate stack are demonstrated even after 1000/spl deg/C postmetal annealing (PMA), which is attributed to the superior oxygen diffusion barrier property of HfN as well as the thermal stability of the HfN-HfO/sub 2/ interface. Therefore, even without surface nitridation prior to HfO/sub 2/ deposition, the EOT of HfN-HfO/sub 2/ gate stack can be successfully scaled down to less than 10 /spl Aring/ after 1000/spl deg/C PMA with excellent leakage and long-term reliability.

Equivalent oxide thickness

Thermal Stability

Metal gate

10.1109/led.2003.820649

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Citations (38)

TASeT: Improving the Efficiency of Electric Taxis With Transfer-Allowed Rideshare

IEEE Transactions on Vehicular Technology (2016)

Yunfei Hou Weida Zhong Lü Su K.F. Hulme Adel W. Sadek

We consider a promising application for electric taxis (eTaxis) in transportation cyberphysical systems. The new rideshare scheme introduced herein takes into consideration both the limited battery of eTaxis and the user requirements. In the proposed eTaxi-sharing system, a passenger may share a taxi with others to enjoy a reduced fare and can potentially transfer from one eTaxi to another before reaching her destination, as long as her total trip time is within the maximum she specifies to be tolerable. Transfers are restricted to only take place at the designated (safe and convenient) battery charging stations scattered around the city. When an eTaxi comes to a charging station to pick up/drop off a transfer passenger, the eTaxi's battery can be charged. In this paper, we address a new optimization problem called Transfer-Allowed Shared eTaxis (TASeT), whose goal is to schedule an eTaxis service and find optimal rideshare and transfer plans to maximize the system throughput in terms of the number of passengers served by the taxi service within a given time period. A mixed-integer programming (MIP) formulation is presented to solve TASeT, along with an efficient greedy heuristic. Aside from large-scale simulation, we also present a case study that utilizes real taxi traces collected from the city of Shanghai, China. Compared with the nontransferable taxi-sharing (NTT) case, our solution could improve the number of served passengers and shared travel distance by 22% and 37%, respectively, during rush hours.

Taxis

10.1109/tvt.2016.2592983

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Citations (15)

Raman selection rules in short-period-superlattice multiple quantum wells

Physics Letters A (1994)

S.L. Zhang Yunfei Hou Kuoksan Ho Peng Zhang J. Li

10.1016/0375-9601(94)90708-0

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Citations (7)

An Automated On-Bed Rehabilitation System Design Based on Pressure Sensory Data Analysis

Qingquan Sun Yunfei Hou Jiang Lu

On-bed physical exercise is significant and necessary during rehabilitation process for patients with motor disorders. An automated, self-managed on-bed rehabilitation system is in demand. Such a system can be achieved and monitored with pressure mapping and posture classification. In this paper we present an automated physical rehabilitation system developed based on pressure mapping and advanced sensory data mining for bed ridden patients to conduct self-rehabilitation. The system is developed with three modules: 1) sensing module; 2) posture recognition module and 3) evaluation ampersand feedback module. Sensing module provides raw data and generates pressure map; Posture recognition module processes pressure data and recognizes postures; Evaluation ampersand feedback module is designed to provide condition evaluations and rehabilitation recommendations. Such a design can automatically provide instructions and guidance for next step exercise, without the involvement of physical therapist. The experimental results have demonstrated the effectiveness of this system. It could serve as a prototype of automated self- rehabilitation system.

10.1109/icaibd57115.2023.10206269

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EdgePS: Selective Parameter Aggregation for Distributed Machine Learning in Edge Computing

Yangming Zhao Yunfei Hou Chunming Qiao

In this paper, we propose EdgePS, an advanced parameter server approach for distributed machine learning in edge computing scenarios. Different from the Conventional Parameter Server (CPS) approach, which performs parameter aggregation after every local training epoch, EdgePS synchronizes the parameters of all workers only when the local training cannot improve the global model performance. We first analyze how the local training will impact the performance of the global model, and then design algorithms to determine when the best time is to perform the parameter aggregation. Both real testbed experiments and extensive large scale simulations demonstrate that EdgePS can train a practical machine learning model, e.g., VGG-16, with up to 59.28% less time compared with the CPS approach. With the same training time, EdgePS can improve model accuracy by up to 30.19 % compared with the state-of-the-art distributed machine learning algorithm designed for edge computing scenarios.

Testbed

10.1109/cloud53861.2021.00035

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Citations (1)

Evaluation of the COVID-19 Shock on STEM Laboratory Courses

2022 IEEE Global Engineering Education Conference (EDUCON) (2021)

Yunfei Hou Fadi Muheidat Timothy Usher Wagner Luiz do Prado Xiaofei Guo

Universities across the U.S. have moved to various virtual teaching models in response to the health threats caused by the COVID-19 pandemic. When converting to an online-only mode, STEM and related fields face additional challenges over the lab portion of courses because laboratory courses and active-learning projects frequently require specialized equipment and manual dexterity interactions. In this paper, we report the results of a study on students' perceptions about online learning during the initial phase of the pandemic at a public university in California, U.S. We focus on the overall reaction to the rapid conversion to online, the negative impressions created, "structural" concerns that would be difficult to mitigate, concerns readily amenable to mitigation, and side effects such as impact on equity. Twenty-five recommendations for those factors deemed improvable are provided.

Pandemic

Equity

2019-20 coronavirus outbreak

Face masks

10.1109/educon46332.2021.9453900

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Citations (15)