本文選題：電學(xué)可靠性 + 氮化鎵　； 參考：《江南大學(xué)》2017年博士論文

【摘要】：由于氮化鎵(GaN)材料具有大禁帶寬度、強(qiáng)擊穿電場、高電子遷移率和高飽和電子漂移速度等優(yōu)越的物理特性,GaN基電子器件比硅基電子器件更適合在高溫、高壓與高頻等極端條件下工作。尤其是基于AlGaN/GaN或晶格匹配In_0.17Al_0.83N/GaN異質(zhì)結(jié)形成的GaN基高電子遷移率晶體管(HEMT),憑借其良好的高頻和大功率特性,成為電力電子、無線通信和雷達(dá)等領(lǐng)域的核心器件。除此之外,GaN材料具有穩(wěn)定的化學(xué)性能,且利用其制備的HEMT檢測器件靈敏度較高,使得近年來GaN基HEMT在生物和光電檢測領(lǐng)域的應(yīng)用也越來越廣泛。但是,盡管GaN基HEMT的性能正不斷取得突破,該器件的大規(guī)模商業(yè)化應(yīng)用仍受到各種電學(xué)可靠性問題的限制。研究此類可靠性問題的物理本質(zhì),推動(dòng)GaN基HEMT在微波功率和檢測領(lǐng)域全面發(fā)展和應(yīng)用,具有非常重要的科學(xué)意義與實(shí)用價(jià)值。鑒于此,本論文較深入地研究了GaN基HEMT中一些重要的電學(xué)可靠性問題,主要包括肖特基特性、電容特性、柵漏電流傳輸機(jī)制以及柵漏電流退化機(jī)制等。首先,根據(jù)實(shí)驗(yàn)需要設(shè)計(jì)并制備了不同結(jié)構(gòu)的器件樣品;然后,綜合運(yùn)用多種光電測試技術(shù)對(duì)樣品進(jìn)行測試;再結(jié)合半導(dǎo)體理論分析測試結(jié)果,深入探究可靠性問題的物理本質(zhì);最后,建立合適的物理模型,并提出了提高器件可靠性的一些可行方法。論文的主要研究內(nèi)容概述如下。1.制備了兩種重要的異質(zhì)結(jié)HEMT器件:AlGaN/GaN HEMT和晶格匹配In_0.17Al_0.83N/GaN HEMT;另外,為了方便研究柵極特性,制備了與HEMT結(jié)構(gòu)柵特性等效的肖特基二極管結(jié)構(gòu)。眾多研究表明,AlGaN/GaN HEMT的制備工藝相對(duì)成熟,但是異質(zhì)界面材料之間晶格不匹配導(dǎo)致的可靠性問題不容忽視;而實(shí)現(xiàn)晶格匹配的In_0.17Al_0.83N/GaN HEMT具有更好的性能,但是由于材料生長比較困難,材料中常存在多種類型的缺陷,因此也會(huì)導(dǎo)致一些新的可靠性問題。本文通過對(duì)這兩種器件的比較分析,對(duì)多個(gè)電學(xué)可靠性問題進(jìn)行了深入的研究。2.研究了GaN基HEMT的反向擊穿行為和正向電流傳輸機(jī)制,有益于提高器件的肖特基特性。盡管In_0.17Al_0.83N/GaN肖特基二極管具有較大的肖特基勢(shì)壘高度,但其反向漏電流較大且反向擊穿電壓較低,發(fā)生了過早擊穿。使用光發(fā)射顯微鏡(EMMI)檢測擊穿后的器件發(fā)現(xiàn),不同于AlGaN/GaN肖特基二極管的縱向擊穿,In_0.17Al_0.83N/GaN肖特基二極管的擊穿方向?yàn)闄M向;InAlN勢(shì)壘層的高密度缺陷是引起過早擊穿行為的主要原因�；诙喾N電流模型對(duì)GaN基HEMT的正向電流進(jìn)行擬合,發(fā)現(xiàn)傳統(tǒng)的熱發(fā)射電流只在體電阻效應(yīng)顯著的高偏壓下占主導(dǎo),低偏電流主要為缺陷輔助隧穿電流。為了全面提高GaN基HEMT肖特基性能,采用合適的鈍化技術(shù)并提高勢(shì)壘層質(zhì)量很有必要。3.表征了GaN基HEMT的異質(zhì)界面缺陷,并解釋了積累區(qū)電容隨頻率增加的反�，F(xiàn)象,有利于提高器件高頻應(yīng)用的可靠性。采用電容-電壓(C-V)平行電導(dǎo)法分析耗盡區(qū)電容頻率散射曲線發(fā)現(xiàn),AlGaN/GaN HEMT異質(zhì)界面存在高密度的淺能級(jí)界面缺陷,缺陷能級(jí)主要集中在0.13eV-0.16eV,而實(shí)現(xiàn)晶格匹配的In_0.17Al_0.83N/GaN HEMT異質(zhì)界面基本不存在界面缺陷。通過測試GaN基HEMT的積累區(qū)C-V變頻曲線,發(fā)現(xiàn)高頻下電容隨頻率的增加而增加,傳統(tǒng)模型無法解釋該現(xiàn)象。通過考慮漏電流、串聯(lián)電阻和界面缺陷等非理想因素,對(duì)傳統(tǒng)模型進(jìn)行了修正;修正后的模型擬合結(jié)果能與實(shí)驗(yàn)結(jié)果很好地吻合,證明該現(xiàn)象是漏電流與界面態(tài)俘獲電子共同作用的結(jié)果。4.澄清了GaN基HEMT反向柵漏電流的傳輸機(jī)制,為進(jìn)一步降低柵漏電流提供了理論指導(dǎo)。在考慮極化電場的影響下,通過驗(yàn)證變溫電流-電壓(I-V)曲線,發(fā)現(xiàn)AlGaN/GaN HEMT的反向電流主要由Frenkel-Poole(FP)發(fā)射機(jī)制主導(dǎo),偏壓繼續(xù)增加,電流逐漸趨于飽和;晶格匹配In_0.17Al_0.83N/GaN HEMT反向低偏電流也為FP發(fā)射電流,但隨偏壓增加,較強(qiáng)的極化電場通過彎曲能帶形成三角勢(shì)壘,發(fā)生Fowler-Nordheim(FN)隧穿。此外,解釋了零偏壓下的電流平衡問題:通過比較極小偏壓下的電流溫度依賴關(guān)系,發(fā)現(xiàn)零偏下的反向電流是被正向隧穿電流抵消的。5.提出了一個(gè)由高場FN隧穿導(dǎo)致GaN基HEMT柵漏電流退化的模型。在無應(yīng)力晶格匹配In_0.17Al_0.83N/GaN HEMT中觀察到柵漏電流的典型退化行為,表明經(jīng)典的逆壓電模型并不是導(dǎo)致GaN基HEMT退化的主要機(jī)制。由此提出一個(gè)新的模型,強(qiáng)調(diào)高場FN隧穿過程釋放的能量通過熱效應(yīng)產(chǎn)生新的缺陷,成為導(dǎo)致柵漏電流退化的主要原因;而退化產(chǎn)生的新缺陷主要在GaN層,可能為N空位。此外,還研究了源-漏應(yīng)力導(dǎo)致的晶格匹配In_0.17Al_0.83N/GaN HEMT柵漏電流退化現(xiàn)象,由于該退化受溫度和柵壓影響明顯,所以溝道熱電子被認(rèn)為是產(chǎn)生退化的主要原因。
[Abstract]:The GaN based electronic devices are more suitable for working in extreme conditions such as high temperature, high pressure and high frequency, especially based on AlGaN/GaN or lattice matching In_0.17Al_0.83N/GaN heterogeneity, because of the advantages of large gap width, strong electric field, high electron mobility and high saturation electron drift speed, and so on. The GaN materials are more suitable for high temperature, high pressure and high frequency than the silicon based electronic devices. GaN based high electron mobility transistor (HEMT) has become the core component in the fields of power electronics, wireless communication and radar, with its good high frequency and high power characteristics. In addition, the GaN material has stable chemical properties, and the sensitivity of the HEMT detection device is high, which makes the GaN based HEMT in biology in recent years. The application of the photoelectric detection field is becoming more and more widespread. However, although the performance of the GaN based HEMT is constantly breaking through, the large-scale commercialized application of the device is still restricted by various electrical reliability problems. The physical essence of this kind of reliability problem is studied, and the GaN based HEMT has been developed and applied in the field of microwave power and detection. It has very important scientific and practical value. In view of this, this paper has studied some important electrical reliability problems in GaN based HEMT, mainly including Schottky characteristics, capacitance characteristics, gate leakage current transmission mechanism and gate leakage current degradation mechanism. First, according to the experiment, different structures are designed and prepared. Then, a variety of photoelectric testing techniques are used to test the samples, and then the physical nature of the reliability problem is explored in depth with the analysis of the results of semiconductor theory. Finally, a suitable physical model is established and some feasible methods to improve the reliability of the device are proposed. The main contents of this paper are summarized as follows:.1. preparation Two important heterojunction HEMT devices: AlGaN/GaN HEMT and lattice matching In_0.17Al_0.83N/GaN HEMT; in addition, in order to facilitate the study of grid properties, the Schottky diode structure equivalent to the HEMT structural grid properties is prepared. Many studies have shown that the preparation process of AlGaN/GaN HEMT is mature, but the lattice mismatch between the heterogeneous interface materials is not matched. The problem of reliability can not be ignored, and the In_0.17Al_0.83N/GaN HEMT for lattice matching has better performance. However, because of the difficult material growth, there are many kinds of defects in the material, so it will also lead to some new reliability problems. In this paper, by comparing and analyzing these two devices, this paper is reliable to multiple electrical reliability. An in-depth study of the sexual problem has been carried out by.2.. The reverse breakdown behavior and forward current transmission mechanism of the GaN based HEMT are studied. It is beneficial to improve the Schottky characteristics of the device. Although the In_0.17Al_0.83N/GaN Schottky diode has a larger Schottky barrier height, the reverse leakage current is larger and the reverse breakdown voltage is low. Through the optical emission microscope (EMMI) detection and breakdown device, it is found that the breakdown direction of the In_0.17Al_0.83N/GaN Schottky diode is transversely different from the longitudinal breakdown of the AlGaN/GaN Schottky diode; the high density defect in the InAlN barrier layer is the main cause for premature breakdown. Based on a variety of current models, the GaN based HEMT is positive. To fit the current, it is found that the traditional heat emission current is dominated by the high bias voltage of the body resistance effect, and the low bias current is mainly a defect auxiliary tunneling current. In order to improve the performance of the GaN based HEMT Schottky, the appropriate passivation technique and the improvement of the barrier layer quality are necessary to characterize the heterogeneous interface deficiency of the GaN based HEMT. It is beneficial to improve the reliability of the high frequency application of the device. The capacitance voltage (C-V) parallel conductance method is used to analyze the capacitance frequency scattering curve of the depleted region. It is found that there is a high density shallow level interface defect in the AlGaN/GaN HEMT heterointerface, and the defect level is mainly concentrated in the 0.13eV-0.16eV The In_0.17Al_0.83N/GaN HEMT heterogeneous interface with lattice matching basically does not exist interface defects. By testing the C-V frequency conversion curve of the accumulation region of GaN based HEMT, it is found that the high frequency capacitance increases with the increase of frequency. The traditional model can not explain this phenomenon. By considering the non ideal factors such as leakage current, serial resistance and interface defect, the traditional model is not ideal. The model is modified, and the corrected model fitting results can be in good agreement with the experimental results. It is proved that the phenomenon is the result of the joint effect of the leakage current and the interface state capture electron..4. clarifies the transmission mechanism of the reverse gate leakage current of the GaN based HEMT, and provides the theoretical guidance for further reducing the gate leakage current. By verifying the temperature variation current voltage (I-V) curve, it is found that the reverse current of AlGaN/GaN HEMT is dominated mainly by the Frenkel-Poole (FP) emission mechanism, the bias voltage continues to increase, the current tends to be saturated, and the lattice matching In_0.17Al_0.83N/GaN HEMT reverse low bias current also emits the current for FP, but with the increase of bias voltage, the stronger polarization electric field passes the bending energy. In addition, the current balance problem under zero bias is explained by forming a triangle barrier and Fowler-Nordheim (FN) tunneling. By comparing the current temperature dependence under the minimum bias voltage, it is found that the reverse current under the zero bias is a positive tunneling current which is offset by the forward tunneling current and presents a model that causes the GaN based HEMT gate leakage current to be degenerated by the high field FN tunneling. The typical degenerate behavior of the gate leakage current in the non stress lattice matching In_0.17Al_0.83N/GaN HEMT shows that the classical reverse piezoelectric model is not the main mechanism leading to the degradation of the GaN based HEMT. A new model is proposed, which emphasizes that the energy overheating effect released by the high field FN tunneling process produces new defects and leads to the gate leakage. The main reason for the degradation of current is that the new defects produced by the degradation are mainly in the GaN layer, which may be N vacancies. In addition, the lattice matching In_0.17Al_0.83N/GaN HEMT gate leakage current degradation caused by the source leakage stress is also studied, because the degradation is affected by the temperature and gate pressure, so the channel thermal electrons are considered to be the main cause of degradation.

【學(xué)位授予單位】：江南大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN386

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