SiN钝化前的NF3等离子体处理对AlGaN/GaN HEMT性能的影响

研究了SiN钝化前利用感应耦合等离子体（ICP）对AlGaN/GaN HEMT表面进行NF3等离子体处理对器件性能的影响. 结果表明,运用低能量的NF3等离子体处理钝化前的AlGaN/GaN HEMT表面能有效抑制器件电流崩塌,而器件直流及微波小信号特性则未受影响. 微波功率测试表明,经过6min NF3等离子体处理的AlGaN/GaN HEMT在2GHz, 30V工作电压下达到6.15W/mm的输出功率密度,而未经过处理的器件只达到1.82W/mm的输出功率密度.     

SiN钝化对W波段AlGaN/GaN HEMT射频性能的影响

在SiC衬底上制备了栅长为110 nm、漏源间距为2μm的W波段AlGaN/GaN高电子迁移率场效应晶体管(HEMT),分析了SiN钝化对器件直流和射频特性的影响.研究发现:100 nm SiN钝化可显著提升器件的漏源饱和电流及峰值跨导,漏源饱和电流从1.27 A/mm增加至1.45 A/mm (Vgs=1 V),器件峰值跨导从300 mS/mm提升至370 mS/mm,这是由于SiN钝化显著提高了AlGaN/GaN异质结材料沟道电子浓度.此外,SiN钝化可有效抑制器件电流崩塌,显著改善器件直流回扫特性.然而,由于沟道电子浓度增大,钝化后器件中短沟效应增强,器件夹断特性变差.此外,SiN钝化后W波段AlGaN/GaN HEMTs的射频特性得到显著改善,器件的电流增益截止频率从钝化前的33 GHz提升至107 GHz,最高振荡频率从钝化前的65 GHz提升至156 GHz.     

钝化与场板结构对AlGaN/GaN HEMT电流崩塌的影响

由于AlGaN/GaN HEMT的几何结构以及很强的极化效应,柵漏区域的电场很大,以至于电子可以从柵隧穿到AlGaN表面.隧穿的电子在表面累积,导致柵下耗尽区的电子向漏端延伸,从而引起漏极电流的下降.文中采用应力测试方法,研究了未钝化、钝化以及场板三种结构的AlGaN/GaN HEMT 的电流崩塌程度.实验结果表明,钝化隔断了电子从柵隧穿到AlGaN表面的通道,场板结构能够有效降低柵边缘电场,均减少了电子从柵隧穿到表面陷阱的几率,从而使虚柵的作用减弱,有效地抑制了电流崩塌效应.     

钝化与场板结构对AlGaN/GaN HEMT电流崩塌的影响

由于AlGaN／GaNHEMT的几何结构以及很强的极化效应,栅漏区域的电场很大,以至于电子可以从栅隧穿到AlGaN表面．隧穿的电子在表面累积,导致栅下耗尽区的电子向漏端延伸,从而引起漏极电流的下降．文中采用应力测试方法,研究了未钝化、钝化以及场板三种结构的AlGaN／GaNHEMT的电流崩塌程度．实验结果表明,钝化隔断了电子从栅隧穿到AlGaN表面的通道,场板结构能够有效降低栅边缘电场,均减少了电子从栅隧穿到表面陷阱的几率,从而使虚栅的作用减弱,有效地抑制了电流崩塌效应．     

Improved Microwave Noise Performance by SiN Passivation in AlGaN/GaN HEMTs on Si

Effects of silicon nitride (SiN) surface passivation by plasma enhanced chemical vapor deposition (PECVD) on microwave noise characteristics of AlGaN/GaN HEMTs on high-resistivity silicon (HR-Si) substrate have been investigated. About 25% improvement in the minimum noise figure $(NF_{min})$ (0.52 dB, from 2.03 dB to 1.51 dB) and 10% in the associate gain $(G_{rm a})$ (1.0 dB, from 10.3 dB to 11.3 dB) were observed after passivation. The equivalent circuit parameters and noise source parameters (including channel noise coefficient $(P)$, gate noise coefficient $(R)$, and their correlation coefficient $(C)$ ) were extracted. $P$ , $R$ and $C$ all increased after passivation and the increase of C contributes to the decrease of the noise figure. It was found that the improved microwave small signal and noise performance is mainly due to the increase of the intrinsic transconductance $(g_{{rm m}0})$ and the decrease of the extrinsic source resistance $(R_{rm s})$.      

AlGaN/GaN HEMT器件的研制

介绍了AlGaN/GaN HEMT器件的研制及室温下器件特性的测试.漏源欧姆接触采用Ti/Al/Pt/Au,肖特基结金属为Pt/Au.器件栅长为1μm,获得的最大跨导为120mS/mm,最大的漏源饱和电流密度为0.95A/mm.     

AlGaN/GaN HEMT器件的研制

介绍了AlGaN/GaNHEMT器件的研制及室温下器件特性的测试.漏源欧姆接触采用Ti/Al/Pt/Au ,肖特基结金属为Pt/Au .器件栅长为1μm ,获得的最大跨导为12 0mS/mm ,最大的漏源饱和电流密度为0 95A/mm .     

AlGaN/GaN double-channel HEMT

The fabrication of AlGaN/GaN double-channel high electron mobility transistors on sapphire substrates is reported. Two carrier channels are formed in an AlGaN/GaN/AlGaN/GaN multilayer structure. The DC performance of the resulting double-channel HEMT shows a wider high transconductance region compared with single-channel HEMT. Simulations provide an explanation for the influence of the double-channel on the high transconductance region. The buffer trap is suggested to be related to the wide region of high transconductance. The RF characteristics are also studied.     

AlGaN/GaN double-channel HEMT

正The fabrication of AlGaN/GaN double-channel high electron mobility transistors on sapphire substrates is reported.Two carrier channels are formed in an AlGaN/GaN/AlGaN/GaN multilayer structure.The DC performance of the resulting double-channel HEMT shows a wider high transconductance region compared with single-channel HEMT. Simulations provide an explanation for the influence of the double-channel on the high transconductance region.The buffer trap is suggested to be related to the wide region of high transconductance.The RF characteristics are also studied.     

Passivation of Surface and Interface States in AlGaN/GaN HEMT Structures by Annealing

The Ni/AlGaN interfaces in AlGaN/GaN Schottky diodes were investigated to explore the physical origin of post-annealing effects using electron beam induced current (EBIC), current–voltage (I–V) characteristics, and X-ray photoelectron spectroscopy (XPS). The EBIC images of the annealed diodes showed that the post-annealing process reduces electrically active states at the Schottky metal/AlGaN interfaces, leading to improvement of diode performance, for example a decrease in reverse leakage current and an increase in Schottky barrier heights. Pulsed I–V characteristics indicate the Fermi level is up-shifted after annealing, resulting in a larger sheet carrier density at the AlGaN/GaN interface. Unintentional oxidation of the free AlGaN surface during the post-annealing process, revealed by XPS analysis, may prevent electron trapping near the drain-side of the gate edges. We suggest that the post-annealing process under an optimized conditions can be an effective way of passivating AlGaN/GaN heterojunction field-effect transistors.     

SiN钝化前的NF3等离子体处理对AlGaN/GaN HEMT性能的影响

研究了SiN钝化前利用感应耦合等离子体(ICP)对AlGaN/GaN HEMT表面进行NF3等离子体处理对器件性能的影响.结果表明,运用低能量的NF3等离子体处理钝化前的AlGaN/GaN HEMT表面能有效抑制器件电流崩塌,而器件直流及微波小信号特性则未受影响.微波功率测试表明,经过6min NF3等离子体处理的AIGaN/GaN HEMT在2GHz,30V工作电压下达到6.15W/mm的输出功率密度,而未经过处理的器件只达到1.82W/mm的输出功率密度.     

Mechanism of Increased High-Frequency Channel Noise With PECVD SiN Passivation in AlGaN/GaN HEMTs

The effect of SiN surface passivation on high-frequency channel noise in AlGaN/GaN high-electron-mobility transistors on a high-resistivity Si substrate is investigated. It was observed that the channel noise increased after SiN surface passivation by plasma-enhanced chemical vapor deposition. The mean square of the channel noise voltage increased about three times at a bias of $V_{d} = hbox{12 V}$ and $I_{d} = hbox{120 mA/mm}$. Based on the analysis on the noise source components in the channel region, it is believed that the channel noise increase is mainly due to the modification of the lateral electrical field profile by surface passivation. The modification of the lateral electrical field profile after passivation is verified by the 2-D numerical simulation and the observation that the gate leakage increases and the breakdown voltage decreases. The measured correlation coefficient between the channel noise and the gate noise agrees with the proposed mechanism of the electrical field profile modification by surface passivation.      

电子辐照对AlGaN/GaN HEMT器件电特性的影响

采用能量为1 MeV的电子对几种不同结构的A1GaN/GaN HEMT器件进行了最高注量为8.575×1014 cm-2的辐照.实验发现:电子辐照后,最高注量下器件欧姆接触性能也几乎没有退化.辐照后来钝化器件的正反向栅电流有所增加,而且肖特基势垒高度随着辐照注量的增加而降低.几种结构HEMT器件的辐照结果表明,电子辐照后只有未钝化器件的特性有所退化,随着辐照注量增加,器件漏电流和跨导下降越明显,而且线性区退化大于饱和区,而阈值电压变化很小.分析表明,HEMT器件参数性能退化的主要原因是栅源和栅漏间隔区辐照感生表面态负电荷的产生.此外实验结果也说明SiN钝化、MOS结构和场板结构都是很好的抗辐照加固的手段.     

Thermal storage effects on AlGaN/GaN HEMT

The effects of thermal storage on GaN–HEMT devices grown on SiC substrate have been investigated by DC and pulsed electrical measurements, breakdown measurements (by means of a Transmission Line Pulser, TLP), and optical and electron microscopy. After 3000 h of thermal storage testing at 300 °C, only a limited reduction of the DC drain saturation current and of the transconductance peak was observed (20% and 25% decrease, respectively). However, pulsed measurements on aged devices clearly highlight a dramatic current collapse effect that has been attributed to a creation of surface traps in the gate-to-drain and gate-to-source access region. On-state breakdown characterization carried out on aged devices did not highlight any noticeable changes with respect to the untreated devices similarly to the DC characterization. Failure analyses have demonstrated that a loss of adhesion of the passivation layer was responsible for the observed trap formation. An improved passivation deposition process was therefore developed, including a surface cleaning procedure aimed at preventing passivation detaching. The devices fabricated using this new procedure do not show any enhancement of trapping effects up to 500 h of thermal stress at 300 °C.     

X-波段AlGaN/GaN HEMT 功率MMIC

AlGaN/GaN高电子迁移率晶体管(HEMT)以其高输出功率密度、高电压工作和易于宽带匹配优势将成为下一代高频固态微波功率器件.     

非掺杂AlGaN/GaN微波功率HEMT

Ga N有较 Ga As更宽的禁带、更高的击穿场强、更高的电子饱和速度和更高的热导率 ,Al Ga N/Ga N异质结构不仅具有较 Ga As PHEMT中Al Ga As/In Ga As异质结构更大的导带偏移 ,而且在异质界面附近有很强的自发极化和压电极化 ,极化电场在电子势阱中形成高密度的二维电子气 ,这种二维电子气可以由不掺杂势垒层中的电子转移来产生。理论上 Al Ga N/Ga N HEMT单位毫米栅宽输出功率可达到几十瓦 ,而且其宽禁带特点决定它可以承受更高的工作结温 ,作为新一代的微波功率器件 ,Al Ga N/Ga N HEMT将成为微波大功率器件发展的方向。采…     

X-波段AlGaN/GaN HEMT功率MMIC

AlGaN/GaN高电子迁移率晶体管(HEMT)以其高输出功率密度、高电压工作和易于宽带匹配等优势将成为下一代高频固态微波功率器件.微波功率器件主要有内匹配功率管和功率单片微波集成电路(MMIC)两种结构形式,功率MMIC尽管其研制成本相对较高,但功率MMIC可实现宽带匹配,同时功率MMIC的体积较内匹配功率管小得多,是满足诸如X波段TlR组件应用不可或缺的结构形式.功率MMIC的结构形式主要有微带和共面波导(CPW)两种,相比于CPW结构,微带结构的MMIC芯片面积更小,特别是对于大栅宽器件,微带结构的通孔接地更有利于寄生参量的减小,有利于提高MMIC的性能,因此微带结构也是应用更为广泛的MMIC结构形式.     

AlGaN/GaN HEMT 2DEG电致耦合模型的研究

传统计算AlGaN/GaN异质结二维电子气(2DEG)的方法是根据Hooke定律计算c轴方向压应变与拉应变,然后利用压电模量计算出不依赖于栅压的2DEG,称为非耦合模型计算.提出了一种电致耦合模型来计算2DEG,在计算过程中考虑到弛豫度与附加电场对材料压电效应的影响,结果发现,当Al组分x=0.30时,压电极化电荷密度低于传统方法的计算值,两种模型的计算值相差7.17%,由此可见,当电场作用于材料时,材料产生逆压电效应,最终导致压电极化电荷密度降低.     

非掺杂AlGaN/GaN微波功率HEMT

报道了研制的AlGaN/GaN微波功率HEMT,该器件采用以蓝宝石为衬底的非掺杂AlGaN/GaN异质结构,器件工艺采用了Ti/Al/Ni/Au欧姆接触和Ni/Au肖特基势垒接触以及SiN介质进行器件的钝化.研制的200μm栅宽T型布局AlGaN/GaN HEMT在1.8GHz,Vds=30V时输出功率为28.93dBm,输出功率密度达到3.9W/mm,功率增益为15.59dB,功率附加效率(PAE)为48.3%.在6.2GHz,Vds=25V时该器件输出功率为27.06dBm,输出功率密度为2.5W/mm,功率增益为10.24dB,PAE为35.2%.     

非掺杂AlGaN/GaN微波功率HEMT

报道了研制的Al Ga N / Ga N微波功率HEMT,该器件采用以蓝宝石为衬底的非掺杂Al Ga N/ Ga N异质结构,器件工艺采用了Ti/ Al/ Ni/ Au欧姆接触和Ni/ Au肖特基势垒接触以及Si N介质进行器件的钝化.研制的2 0 0μm栅宽T型布局Al Ga N / Ga N HEMT在1.8GHz,Vds=30 V时输出功率为2 8.93d Bm,输出功率密度达到3.9W/mm ,功率增益为15 .5 9d B,功率附加效率(PAE)为4 8.3% .在6 .2 GHz,Vds=2 5 V时该器件输出功率为2 7.0 6 d Bm ,输出功率密度为2 .5 W/ mm ,功率增益为10 .2 4 d B,PAE为35 .2 % .