本文選題：AlGaN/GaN + 溫度特性　； 參考：《西安電子科技大學(xué)》2015年碩士論文

【摘要】：由于Ga N材料具有許多杰出的特性,例如高的擊穿場強、高的面電荷密度和高的電子遷移率,使得AlGaN/GaN HEMTs器件已經(jīng)廣泛地應(yīng)用于高頻和高功率領(lǐng)域,而溫度可靠性是阻礙器件進(jìn)一步發(fā)展的關(guān)鍵問題之一,所以為了提升器件的性能,研究器件的溫度特性是十分必要的。在這樣的研究背景下,本篇論文將主要圍繞Ga N基器件的變溫特性尤其是低溫下器件的特性展開研究。論文利用Silvaco軟件對器件的變溫特性進(jìn)行了仿真,首先介紹了Silvaco的基本模型及數(shù)值計算方法,然后對比了不同器件結(jié)構(gòu)的導(dǎo)帶圖差異。接著分別研究了器件在不同溫度下的電場分布和熱分布特性,發(fā)現(xiàn)隨著溫度的降低,電場強度減弱。在150K~450K溫度范圍內(nèi)對晶格溫度進(jìn)行了提取,發(fā)現(xiàn)器件的強場高溫點基本上位于器件柵極靠近漏極一側(cè)的亞微米區(qū)域,并提出了降低結(jié)溫和減小自熱效應(yīng)的方法。接著,在低溫77K~200K范圍內(nèi)對器件的輸出和轉(zhuǎn)移特性進(jìn)行了仿真,發(fā)現(xiàn)隨著溫度的降低,器件的飽和輸出電流增大,跨導(dǎo)峰值增加。從轉(zhuǎn)移曲線中又進(jìn)一步得到了閾值電壓隨溫度的變化關(guān)系,由于閾值電壓主要與二維電子氣的密度有關(guān),所以利用1D Possion仿真軟件在50K~500K溫度下對2DEG的濃度及AlGaN和Ga N的導(dǎo)帶差進(jìn)行了仿真,發(fā)現(xiàn)隨著溫度的降低導(dǎo)帶差增大,所以低溫下溝道電子數(shù)量增多。此外,還進(jìn)一步分析了Al組分和勢壘層厚度對2DEG濃度的影響。論文在77K~270K下對Al Ga N/GaN HEMT器件進(jìn)行了低溫直流特性測試,對器件的輸出特性和轉(zhuǎn)移特性分別進(jìn)行了分析,得到的結(jié)論與仿真結(jié)果相當(dāng)吻合。并用TLM測量的方法研究了溫度對電子遷移率的影響,發(fā)現(xiàn)遷移率隨溫度的降低而增大,并對影響電子遷移率的不同散射機(jī)制進(jìn)行了簡要說明。論文還利用DLTS(深能級瞬態(tài)譜儀)對器件的變溫C-V特性和陷阱特性進(jìn)行了測試和分析,發(fā)現(xiàn)隨著溫度的降低器件的閾值電壓正向漂移這一反常現(xiàn)象,認(rèn)為可能是由于界面態(tài)陷阱的影響導(dǎo)致了C-V曲線的不穩(wěn)定,我們通過Arrenius分析對陷阱進(jìn)行了表征,并推測出陷阱的類型,確定了陷阱的能級位置和俘獲截面。論文在400K-120K溫度范圍內(nèi)對AlGaN/Ga N器件的正反向柵漏電特性進(jìn)行了研究,用熱電子發(fā)射模型提取了理想因子和肖特基勢壘高度。發(fā)現(xiàn)當(dāng)溫度低于200K時,漏電流幾乎不隨溫度變化,因此推斷出FN(Fowler-Nordheim)隧穿機(jī)制是低溫下漏電的主導(dǎo)機(jī)制。對反向漏電機(jī)制用FP(Frenkel-Poole)發(fā)射和FN隧穿模型分別進(jìn)行了分析,提取出的高頻介電常數(shù)4)和陷阱勢壘高度與相關(guān)報道非常吻合。
[Abstract]:Due to many outstanding characteristics of gan, such as high breakdown field strength, high surface charge density and high electron mobility, AlGaN/GaN HEMTs devices have been widely used in high frequency and high power fields. The temperature reliability is one of the key problems that hinder the further development of the device, so in order to improve the performance of the device, it is very necessary to study the temperature characteristics of the device. In such a background, this thesis will focus on the characteristics of gan based devices at variable temperature, especially at low temperature. In this paper, the variable temperature characteristic of the device is simulated by Silvaco software. Firstly, the basic model and numerical calculation method of Silvaco are introduced, and then the difference of the conduction band diagram of different device structures is compared. Then the electric field distribution and thermal distribution of the device at different temperatures are studied, and it is found that the electric field intensity decreases with the decrease of temperature. The lattice temperature is extracted in the range of 150K~450K temperature. It is found that the high temperature point of the device is basically located in the sub-micron region near the drain side of the gate of the device, and a method to reduce the junction temperature and reduce the self-heating effect is proposed. Then, the output and transfer characteristics of the device are simulated in the range of low temperature 77K~200K. It is found that the saturation output current increases and the transconductance peak increases with the decrease of temperature. The relationship between threshold voltage and temperature is further obtained from the transfer curve, because the threshold voltage is mainly related to the density of two-dimensional electron gas. So the concentration of 2DEG and the conduction band difference between AlGaN and gan are simulated at 50K~500K temperature by using 1D Possion simulation software. It is found that the number of channel electrons increases with the decrease of temperature. In addition, the effects of Al composition and barrier thickness on the concentration of 2DEG were further analyzed. In this paper, the low-temperature DC characteristics of Al Ga N/GaN HEMT devices are tested under 77K~270K. The output characteristics and transfer characteristics of the devices are analyzed, and the results are in good agreement with the simulation results. The effect of temperature on electron mobility is studied by TLM measurement. It is found that the mobility increases with the decrease of temperature, and the different scattering mechanisms affecting electron mobility are briefly explained. DLTS (deep level transient spectrometer) is also used to test and analyze the variable-temperature C-V and trap characteristics of the device. It is found that with the decrease of temperature, the positive drift of the threshold voltage of the device is abnormal. It is suggested that the instability of C-V curves may be due to the influence of interfacial state traps. We characterize the traps by Arrenius analysis, infer the types of traps, and determine the energy level positions and trapping cross sections of traps. In this paper, the forward and backward gate leakage characteristics of AlGaN/Ga N devices are studied in the 400K-120K temperature range. The ideal factor and Schottky barrier height are extracted by using the hot electron emission model. It is found that the leakage current almost does not change with the temperature when the temperature is below 200K, so it is inferred that the FNN Fowler-Nordheimm) tunneling mechanism is the dominant mechanism of leakage at low temperature. The reverse leakage mechanism is analyzed by FPN Frenkel-Poole emission model and FN tunneling model respectively. The extracted high frequency dielectric constant 4) and trap barrier height are in good agreement with the related reports.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN386

【參考文獻(xiàn)】

相關(guān)期刊論文 前3條

1 鄭佳欣;馬曉華;盧陽;趙博超;張宏鶴;張o，

本文編號：1878173