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Design and Simulation of High Performance Lattice Matched Double Barrier Normally Off AlInGaN/GaN HEMTs
(2020-01-01)
Shrestha, Niraj Man
;
Li, Yiming
;
Chen, Chao-Hsuan
;
Sanyal, Indraneel
;
Tarng, Jenn-Hawn
A novel lattice matched double barrier Al0.72In0.16Ga0.12N/Al0.18In0.04Ga0.78N/GaN normally-off high electron mobility transistor (HEMT) is designed and simulated by solving a set of thermodynamic transport equations. Using the experimentally calibrated physical models with bearing mobility degradation by surface roughness in account, the recess gate and double barrier of the proposed device achieves a maximum drain current density (I-D,I-max) of 1149 mA/mm and a maximum transconductance (g(m,max)) of 358 mS/mm with a positive threshold voltage (Vth) of 0.2 V. The small polarization charge of first barrier is responsible for positive Vth. I-DS,I-max in the double barrier HEMT at high gate bias condition is due to injection of electrons from upper 2DEG which is almost impossible at lower gate voltage because of insufficient energy to cross the barrier. The injection of electrons is further supported by the second peak in the g(m) curve at low gate bias V-G = 1V. The outcome of this study suggests that the proposed device will be beneficial for high-frequency and high-power electronic applications.
SiC Strained nMOSFETs With Enhanced High- Frequency Performance and Impact on Flicker Noise and Random Telegraph Noise
(2020-06-01)
Guo, Jyh-Chyurn
;
Chang, Chih-Shiang
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Silicon-carbon (SiC) strained nMOSFETs with sub35-nm gate length in a 40-nm CMOS technology can realize superior cutoff frequency (f(T)) up to 405 GHz, attributed to more than 20% enhancement of the mobility and transconductance. This super-400-GHz f(T) makes SiC strained nMOS an attractive high mobility device aimed at millimeter-wave (mm-wave) CMOS circuits design. However, the SiC nMOSFETs reveal a dramatic increase in flicker noise and random telegraph noise (RTN), which may cause worse phase noise and detrimental impact on CMOS oscillator stability. The complex RTN features abnormally long capture and emission time constants (tau(c) and tau(e)) and suggests electron-phonon coupling responsible for the anomalously slow trapping and detrapping, due to a significant increase of relaxation energy from SiC strain. This critical tradeoff between high-frequency performance and low-frequency noise becomes a key factor to be considered for the most appropriate adoption of high mobility devices and design optimization adapted to various circuits.
Electrical Characteristic of AlGaN/GaN High-Electron-Mobility Transistors With Recess Gate Structure
(2019-04-01)
Shrestha, Niraj Man
;
Li, Yiming
;
Suemitsu, Tetsuya
;
Samukawa, Seiji
;
交大名義發表
AlGaN/GaN high-electron-mobility transistors (HEMTs) with nonrecess and recess gates are simulated by solving a set of drift-diffusion equations for electrostatic potential and electron-hole concentrations with self-heating model. The approach is first calibrated for both HEMT devices with experimentally measured data, to provide the best accuracy of the simulation. Recess gate device suffers from high potential to the channel, increased parasitic resistances, and deep level traps in barrier due to surface roughness. In addition, selective thinning of the barrier and increase parasitic resistance results in 17% reduction on the carrier concentration. The carrier mobility degradation due to surface roughness and electron velocity lessen due to high electric field result shrinkage of current density with considerable shift of the threshold voltage toward positive value. Even though transconductance does not seems to be remarkably changed for 3-nm recess gate, its value increases on deeper recess. This paper reveals that surface roughness is crucial issue that has dominant role behind the low current density in the recess gate structure. The detail physical understanding of the recess technology will be helpful to minimize the performance deterioration of the explored devices.
Mobility enhancement in local strain channel nMOSFETs by stacked a-Si/poly-Si gate and capping nitride
(2005-04-01)
Lu, TY
;
Chao, TS
;
交大名義發表
;
National Chiao Tung University
A local strained channel nMOSFET has been fabricated by a stress control technique utilizing a stacked a-Si/poly-Si gate and a SiN capping layer. It is found that the transconductance (G(M)) of nMOSFETs increases as the thickness of a-Si is increased. We also found that the G(M) of devices with the SiN capping layer exhibits a 17% increase compared to that of its counterparts. The stacked gate a-Si/poly-Si with the capping layer can improve the G(M) further to 29% more than the single-poly-Si gate structure without SiN capping layer.
Modeling and Analysis of Channel Holding Time and Handoff Rate for Packet Sessions in All-IP Cellular Networks
(2017-04-01)
Ku, Bying-He
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Ren, Yi
;
Weng, Jeng-Feng
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Chen, Jyh-Cheng
;
Chen, Wen-Tsuen
It is essential to model channel holding time (CHT), cell residence time (CRT), and handoff rate for performance analysis and algorithm evaluation in mobile cellular networks. The problem has been extensively studied in the past for circuit-switched (CS) cellular networks. However, little research has been done on packet-switched (PS) cellular networks. Unlike that a call occupies a dedicated channel during its whole lifetime in CS networks, an active session in PS networks occupies and releases channels iteratively due to discontinuous reception (DRX) mechanism. In this paper, we investigate the key quantities in PS cellular networks. We present a set of comprehensive new models to characterize the quantities and their relationship in PS networks. The models shed light on the relationship between CHT and CRT and handoff rate. The analytical results enable wide applicability in various scenarios and therefore have important theoretical significance. Moreover, the analytical results provide a quick way to evaluate traffic performance and system design in PS cellular networks without wide deployment, which can save cost and time.
DC/AC/RF Characteristic Fluctuations Induced by Various Random Discrete Dopants of Gate-All-Around Silicon Nanowire n-MOSFETs
(2018-06-01)
Sung, Wen-Li
;
Li, Yiming
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, we explored the characteristic fluctuations induced by various random discrete dopants (RDDs) on gate-all-around silicon nanowire metal-oxide semiconductor field-effect transistors. A 3-D quantum-mechanically corrected transport model was employed to analyze the simulated devices. The statistical results indicate that the variation of threshold voltage (Vth) not only can be reduced from 28.6% to 10.7% without channel doping and penetration from the source/drain into the channel, but also the variation of 3-dB frequency can be reduced from 8% to 2.7% due to the reduction of the variation of Vth. We reported that the high-frequency characteristic fluctuations (voltage gain and cutoff frequency) were dominated by electron mobility. This caused by RDDs from the drain extension exhibited less variability than that caused by RDDs from the source extension due to a reduced injection velocity near the S side and a negligible difference in the electron saturation velocity near the D side. This paper provides pertinent information on the design of high-frequency amplifier circuits in relation to devices with RDDs induced by variations in the semiconductor process.
Rational Design of ZnO:H/ZnO Bilayer Structure for High Performance Thin-Film Transistors
(2016-03-30)
Abliz, Ablat
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Huang, Chun-Wei
;
Wang, Jingli
;
Xu, Lei
;
Liao, Lei
The intriguing properties of zinc oxide-based semiconductors are being extensively studied as they are attractive alternatives to current silicon-based semiconductors for applications in transparent and flexible electronics. Although they have promising properties, significant improvements on performance and electrical reliability of ZnO-based thin film transistors (TFTs) should be achieved before they can be applied widely in practical applications. This work demonstrates a rational and elegant design of TFT, composed of poly crystalline ZnO:H/ZnO bilayer structure without using other metal elements for doping. The field-effect mobility and gate bias stability of the bilayer structured devices have been improved. In this device structure, the hydrogenated ultrathin ZnO:H active layer (similar to 3 nm) could provide suitable carrier concentration and decrease the interface trap density, while thick pure-ZnO layer could control channel conductance. Based on this novel structure, a high field-effect mobility of 42.6 cm(2) V-1 s(-1), a high on/off current ratio of 108 and a small subthreshold swing of 0.13 V dec(-1) have been achieved. Additionally, the bias stress stability of the bilayer structured devices is enhanced compared to the simple single channel layer ZnO device. These results suggest that the bilayer ZnO:H/ZnO TFTs have a great potential for low-cost thin-film electronics.
High-Performance Submicrometer ZnON Thin-Film Transistors With Record Field-Effect Mobility
(2016-03)
Kuan, Chin-I
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Lin, Horng-Chih
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Li, Pei-Wen
;
Huang, Tiao-Yuan
;
電子工程學系及電子研究所
In this letter, we demonstrate 0.6-mu m ZnON thin-film transistors (TFTs) with the field-effect mobility of 71 cm(2)/V-sec, which to the best of our knowledge is the highest value ever reported on submicrometer oxide-semiconductor TFTs. The drive current, field-effect mobility, and subthreshold slope of ZnON TFTs are significantly improved as compared with their counterpart ZnO TFTs of the same channel dimensions and structure. Such an improvement in the field-effect mobility primarily results from a considerable reduction in the series source/drain (S/D) resistances because of suppression in an interfacial layer formation between Al S/D pads and the channel layer.
Channel Holding Time of Packet Sessions in All-IP Cellular Networks
(2014)
Weng, Jeng-Feng
;
Ku, Bying-He
;
Chen, Jyh-Cheng
;
Chen, Wen-Tsuen
;
資訊工程學系
In this paper, we analyze the packet session channel holding time for packet-switched cellular networks. Channel holding time depends on mobility which is characterized by cell residence time in this paper. We apply Hyper-Erlang distribution model to investigate the packet session channel holding time in which a session will experience active and idle periods. In terms of new session, handoff session in busy mode, handoff session with new arrival packets in idle mode and handoff session without arrival packet in idle mode, we demonstrate that the effective channel holding time is exponentially distributed if and only if the cell residence time is exponentially distributed. The analytical results provide a new approach to evaluate traffic performance and system design in packet-switched cellular networks.
異質網路環境之行動搜尋關鍵技術---總計畫
(2008)
簡榮宏
;
JAN RONG-HONG
;
國立交通大學資訊工程學系(所)
網際網路的搜尋(web search)，目前正漸漸轉移到電信服務上，全球知名的電信服務業者相繼加入。然行動搜索(Mobile Search) 受限於手機裝置諸多限制，無法有效的在異質性的行動無線網路環境下運作，急需要整合性的技術。有鑑於此，本計畫的總目標在於設計與研發行動搜尋之應用及網路平台，並針對下列五個研究課題，分五個子計畫執行：1) 車用隨意網路之存取控制與連結機制; 2) 車用隨意網路之資訊整合、散佈、傳輸與群播技術; 3) 行動無線感測網路連結機制之研發; 4) 以感測系統為基礎之整合式室內及室外定位系統;5) 行動搜尋資料淬取與探勘機制。並透過總計畫加以整合。子計畫一的主要研究目標在於發展VANET網路之存取控制協定(Media Access Control, MAC)及連結機制(Connectivity Support)。分為三個階段:在第一年的計畫中，先針對網路低層的MAC進行設計，我們將基於未來最有可能被廣泛使用的DSRC標準進行發展，以合乎趨勢的走向。接下來，在第二年的研究裡，我們將為高速移動的車輛設計以有效的叢集化及功率指定方法，以減少網路干擾，進而提升流量產出及管理上的效果。基於這些低層的技術及規劃方法後，最後一年，我們將發展上層的路由及配送方法，以可克服VANET網路因高度移動和短距離傳輸所造成間歇性連結特性及其衍伸的延遲問題，達到可靠傳輸的最終目標。子計畫二主要的研究目標是使資訊在車用隨意網路中能快速、可靠且有效的傳播。而本計畫主要的研究課題為: (1)在車用隨意網路中如何能在特定的時間內與空間中快速整合、散佈、複製和儲存資訊。(2)由於車用隨意網路有容遲網路之特性，我們也將探討TCP在容遲網路中的運作困難以及解決方法，以達成資訊可靠的傳輸。(3)最後則是研究車用隨意網路的群播協定以達成資訊有效的傳播。子計畫三目標是要提供與維護無線感測網路的連結性。主要的研發主題有二: (1)動態無線感測網路建構與維護，(2)含具電節點之動態無線感測網路建構與維護。第一個研發主題以支援感測網路節點的移動性為目標，開發識別碼分配、繞送以及單一或群體節點漫遊機制，此外為了減少熱點現象所造成的問題，也會發展平衡網路流量的負載平衡機制，同時為了解決節點耗損造成網路失連的情形，也會研發容錯機制。第二個研發主題則以發展具電節點為路由節點的繞送機制為主，以解決熱點傳輸產生的耗電問題，同時也會研發具電節點的容錯遊機制以及具電節點漫遊或以具電節點為路由節點的群體漫遊機制，以維護整個網路的連結性。子計畫四之目的在於提供隨時隨地可取得準確性高的定位服務，以提供各類網路系統及位置感知服務系統運作所需的位置資訊。我們將透過分析微型感測元件（如：加速度計、角速度計、電子陀螺儀及磁力計等）的量測資料及配合現有的室內及室外定位系統達成下列四個研究成果：(1)以低廉的成本達到改善全球定位系統（GPS）的精確度；（2）改善室內定位系統的精確度；(3)利用無線網路通訊技術，發展團隊導航功能；(4)以個人定位系統為基礎，開發可還原汽車運動軌跡之車輛行進記錄器。子計畫五的主要的研究目標將提出一個整合性的行動搜尋環境，有鑑於 Web 2.0 有用得資訊與豐富的網頁知識，我們將結合Web2.0及網路上的社群結構，提供使用者有用的資料，並將研發資料探勘技術，分析使用者的行為模式，用以預測使用者的行為模式，減少手持式裝置的輸入不便。本計畫中，我們主要的研究課題為 (1). 從 Web 2.0 網站進行一資料的重整，將地理物件如餐廳或是景點，進行資料淬取，以整理出結構化之資料形式，提供行動搜尋之內容。 (2).針對 Web 2.0 網站，進行社群探勘，以便提供行動搜尋更為有用且精準的資訊。(3). 研發使用者行為探勘機制，以主動提供資料，將行動搜尋得整體使用效率達到最佳化。表

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