不同陽極蝕刻深度之氮化鋁鎵/氮化鎵蕭特基二極體特性分析

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Title:	不同陽極蝕刻深度之氮化鋁鎵/氮化鎵蕭特基二極體特性分析
Authors:	范姜少琪;Jiang, Shao-Chi Fan
Contributors:	電機工程學系
Keywords:	氮化鋁鎵/氮化鎵;蕭特基二極體;陽極蝕刻
Date:	2018-08-06
Issue Date:	2018-08-31 14:54:34 (UTC+8)
Publisher:	國立中央大學
Abstract:	本論文主要針對在矽(111)基板上製作不同陽極蝕刻深度之氮化鋁鎵/氮化鎵蕭特基二極體。一般蕭特基二極體為了降低開關過程中的損耗，降低臨界電壓與保持低的漏電流是相當重要的議題，而本論文將針對降低開啟電壓進行研究。首先，利用TCAD的模擬分析無陽極蝕刻(Device A)、陽極蝕刻深度至AlGaN位障層(Device B)、陽極蝕刻深度超過2DEG介面之蕭特基二極體基本電性。接著探討其製程後的特性表現，利用室溫下的電容-電壓的量測曲線，分析不同陽極蝕刻深度與通道中的2DEG濃度關聯性，以及室溫下順向、逆向電流-電壓特性分析。當陽極蝕刻深度至AlGaN位障層，其臨界電壓(VT )為1.05 V，且藉由陽極端金屬的T型設計分散邊緣的電場，而有較高的崩潰電壓480 V。當陽極蝕刻深度超過2DEG介面，其臨界電壓(VT )達到最低0.75 V。也利用變溫來探討氮化鋁鎵/氮化鎵蕭特基二極體順向偏壓及逆向偏壓下的特性，在順向偏壓下藉由不均勻能障模型來計算蕭特基能障，估算蒸鍍金屬後的蕭特基接觸有不均勻的接面。而逆向電流-電壓曲線可以進一步分析漏電流機制，因低溫下缺陷中之載子不易產生變化，而在高溫下載子就容易因為溫度的關係而從缺陷中逃脫。量測得知，漏電流皆會隨著電場和溫度而變化，而在較高逆偏壓下漏電流則與溫度無相依性，而是與電場相關，此種漏電流受溫度及電場影響之電流機制為Frenkel–Poole emission。其中Device B有較大的漏電流，推測原因可能是由於蝕刻後表面不平整及缺陷而造成較大的漏電流，其缺陷能階估算位在導電帶下方0.03 eV。但在Device A中，其缺陷能階估算位在導電帶下方1.19 eV，因只有表面Si3N4的蝕刻導致缺陷的原因不同。 ;GaN-based heterostructure lateral Schottky barrier diodes (SBDs) grown on Silicon (111) substrate with various recess depths are investigated in this study. Conduction losses in onset voltage and reverse-bias leakage result in significant limitations to power switching performance of Schottky diodes. First of all, Silvaco TCAD was used to simulate the electrical properties of Schottky barrier diodes with various recess depths. Three diode structures are investigated, Device A is the SBD without recess in AlGaN layer, Device B is the SBD with a 20-nm recess depth in AlGaN layer (1.6 nm left) and Device C is the SBD with whole AlGaN layer removed and recessed to GaN layer. After SBD fabrication, both C-V and I-V characteristics at room temperature are analyzed. The results reveal that Device B shows threshold voltage (VT) of 1.05 V and reverse blocking voltage of 480 V. The SBD with recess through AlGaN to GaN layer demonstrates the lowest VT of 0.75 V. Furthermore, temperature dependence of forward and reverse current-voltage characteristics of AlGaN/GaN SBDs are investigated. In forward bias condition, considering the alloy composition fluctuations inherent to low-temperature III-N alloys which results in a Schottky barrier height inhomogeneity, and that the Schottky barrier height follows a Gaussian distribution. By observing the reverse bias leakage current flow, it is possible to find the defect energy levels in AlGaN barrier are quantified by the leakage current model of Frenkel-Poole emission. Frenkel-Poole emission refers to electric-field-enhanced thermal emission from a trap state into a continuum of electronic states. Device B has larger leakage current due to stronger surface roughness (damages) that the trap state to be located 0.03 eV below the conduction-band edge. In the Device A, due to the in-situ SiN was removed before gate metallization that the trap state to be located 1.19 eV below the conduction-band edge.
Appears in Collections:	[Graduate Institute of Electrical Engineering] Electronic Thesis & Dissertation

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