砷化銦/銻化鋁高電子遷移率場效電晶體製程開發與元件特性之研究; Device Fabrication and Characterization of InAs/AlSb High Electron Mobility Transistors

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题名:	砷化銦/銻化鋁高電子遷移率場效電晶體製程開發與元件特性之研究;Device Fabrication and Characterization of InAs/AlSb High Electron Mobility Transistors
作者:	林育昭;Yu-Chao Lin
贡献者:	電機工程研究所
关键词:	砷化銦/銻化鋁;扭結效應;高電子遷移率場效電晶體;InAs/AlSb;HEMT;kink effect
日期:	2009-07-03
上传时间:	2009-09-22 12:16:03 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	InAs因擁有高電子遷移率、高電子飽和速度及低能隙，故適於應用在低功率和高速的電子元件；然而，在高電場下引發衝擊離化所產生的電洞將因InAs/AlSb的第二型能帶對齊方式而無法侷限於通道層，造成了元件輸出電導隨著汲極電壓上升而增加的缺點。本論文除了敘述元件的製程發展和探討元件特性外，也提出改善元件kink效應的方式。製程發展包含歐姆接觸、元件隔離與鈍化製程。在300 ℃維持20秒的快速熱退火條件可製作出低於0.1 Ω-mm的歐姆接觸電阻；透過元件隔離製程後隨即覆蓋SiO2鈍化層改善了AlxGa1-xSb材料所造成的不穩定及元件漏電流。傳統Si3N4鈍化實驗上則得到的最佳鈍化條件為300 ℃。元件特性上，在超薄n+-InAs摻雜及SiO2鈍化的元件可得到103.3 mV/dec的次臨界斜率；閘極長度為2.25 mm的元件得到63 GHz-mm的fT - Lg乘積，而Si3N4鈍化後，Te面摻雜的元件之汲極電流可到達320 mA/mm。在kink效應的改善上，透過InAsSb/AlSb HEMT的第一型能帶對齊方式可有效地將kink電流從汲極電壓為0.35 V改善至0.6 V。最後也設計不同的場效電板(Field plate)來抑制InAs/AlSb HEMT元件上的kink效應。 High mobility, high peak velocity, and small bandgap associated with the InAs channel material are suitable for low power and high speed applications. However, large amount of holes are generated by impact ionization and result in serious kink effect and increased gate currents. In the thesis, we develop processes for device fabrication and characterize dc and rf properties of the InAs/AlSb HEMTs. The device development includes ohmic contact, mesa isolation, and passivation. Using rapidly thermal annealing at 300 ℃ for 20s, ohmic contact resistance as low as 0.1 Ω-mm is achieved. To improve chemical stability of mesa floor and side wall, we perform 1st passivation immediately after defining the device mesa. Gate leakage is thus improved. Optimized passivation condition for conventional Si3N4 passivant deposited after Schottky gate is 300 ℃. For the HEMT structure using a thin n+-InAs as modulation doping sheet and fabricated by the developed passivation scheme, low subthreshold slope of 103.3 mV/dec. and high fT - Lg product of 63 GHz-mm is obtained in a device with 2.25 mm gate length. It is observed the device with Si3N4 passivation yields enhanced driving current, which are attributed to increased carrier density and electric field. As for the kink current improvement, type-I InAsSb/AlSb HEMTs and implementation of dual gate both effectively improve the kink effect.
显示于类别:	[電機工程研究所] 博碩士論文

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