具背閘極之氮化鋁鎵/氮化鎵高電子遷移率電晶體;AlGaN/GaN HEMTs with Backgate Structure

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題名:	具背閘極之氮化鋁鎵/氮化鎵高電子遷移率電晶體;AlGaN/GaN HEMTs with Backgate Structure
作者:	林瑋哲;Lin, Wei-Tse
貢獻者:	電機工程學系
關鍵詞:	氮化鋁鎵/氮化鎵;背閘極;臨界電壓;漏電流;AlGaN/GaN;backgate;threshold voltage;leakage current
日期:	2017-07-26
上傳時間:	2017-10-27 16:11:19 (UTC+8)
出版者:	國立中央大學
摘要:	本論文探討背閘極結構對氮化鋁鎵/氮化鎵高電子遷移率電晶體電性的影響，內容分為兩個主題， (1) 使用氮化鋁鎵/氮化鎵/氮化鋁鎵雙異質結構磊晶層製作的二維電洞氣背閘極電晶體，透過偏壓二維電洞氣背閘極研究元件漏電流與臨界電壓的改變。(2) 使用p-型氮化鎵背閘極之氮化鋁鎵/氮化鎵電晶體，元件製作前先經過700度15分鐘氮氣環境中進行熱退火，利用p-型氮化鎵磊晶的活化與否，研究不同背閘極偏壓對元件的臨界電壓、漏電流和崩潰電壓影響。從元件模擬結果可觀察出以二維電洞氣為背閘極並透過偏壓控制使元件由空乏型(depletion-mode operation)變成加強型工作模式(enhancement-mode operation)並改善元件漏電流是可行的。但元件因為背閘極蝕刻深度和背閘極電極製作，無法得到背閘極和準確控制和二維電洞氣間的有效連接，使元件在臨界電壓的控制上無法如模擬的結果。但背閘極金屬施加的負偏壓依然可藉由較大的電場抑制元件的漏電流，元件在不同背閘極偏壓下開關電流比值皆可達到107等級，元件崩潰電壓也可以達到691 V。具p-型氮化鎵背閘極之氮化鋁鎵/氮化鎵高電子遷移率電晶體在元件直流特性的量測上，未經退火製程元件有較低的漏電流與導通電阻，經過退火製程元件在背閘極偏壓控制上有更明顯的抑制漏電流和臨界電壓的正向偏移。在背閘極偏壓從0 V增加到-14 V時，未經退火製程的元件之臨界電壓向正偏移0.46 V，關閉時漏電流降低了42.6% ；經過退火製程的元件之臨界電壓向正偏移0.55 V，關閉時漏電流降低了73.1% 。兩種元件在背閘極偏壓為0 V的開關電流比值分別為 (〖I_on/I_off )〗_(with activation )= 8.86×105、(〖I_on/I_off )〗_(without activation )= 5.47×107 。經過退火的元件在背閘極偏壓為-14 V時開關電流比可提升至1.12×107。在崩潰電壓上，經過退火製程的元件有較強的耐壓，未經退火製程的元件在元件達到崩潰電壓前有較低的漏電流。經過退火製程的元件且背閘極偏壓為-14 V時，呈現最好的崩潰電壓762 V。 ;This study discusses the impact of back-gate structure on the DC characteristics of an AlGaN/GaN high-electron mobility transistor (HEMT). There are two parts in this study: (1) An AlGaN/GaN/AlGaN double heterostructure is designed to form two dimensional electron gas (2DEG) channel and two dimentional hole gas (2DHG) backgate and investigate the reduction of leakage current with shift of threshold voltage when backgate bias is applied. (2) AlGaN/GaN HEMTs with p-GaN backgate were annealed for 15 minutes in N2 ambient at 700℃. After annealing, we investigate the ability of activated p-GaN backgate layer for controling threshold voltage, reducing leakage current, and enhancing breakdown voltage. The results of simulation reveal that 2DHG backgate can decrease leakage current and turn device from depletion-mode operation to enhancement-mode operation by applying backgate bias. However, the fabricated devices do not demonstrate the same control capibility of threshold voltage as simulation due to the bad connection between backgate metal and 2DHG. The large electric field induced by backgate still can suppress device leakage current when a negative bias is applied. The on/off current ratio in different backgate bias can achieve 107. In addition, device breakdown voltage of 691 V is observed. For the DC characteristic of AlGaN/GaN HEMTs with p-GaN backgate, devices without annealing have lower leakage current and on-state resistance. Devices with annealing show higher leakage current and more obvious positive shift of threshold voltage. The shift of threshold voltage for device without annealing is 0.46 V between backgate bias 0 V and -14 V, and off-state leakage current reduction is 42.6%. The shift of threshold voltage for device with annealing is 0.55 V between backgate bias 0 V and -14 V, and off state leakage current reduction is 73.1%. The on/off current ratio for device without annealing is 5.47×107, and 8.86×105 for device with annealing when backgate bias apply 0 V. Current ratio for device with annealing can increase to 1.12×107 when backgate bias at -14 V. Devices without annealing show lower leakage current before devices breakdown. However, devices with annealing show higher breakdown voltage. The highest breakdown voltage is 762 V for device with annealing when applying backgate bias of -14 V.
顯示於類別:	[電機工程研究所] 博碩士論文

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