版图设计对多指AlGaN/GaN HEMTs 栅指温度影响的研究

本文利用三维热仿真方法研究了不同版图设计对多指AlGaN/GaN 高电子迁移率器件工作温度的影响。我们使用拉曼微区测温技术测量了样品的沟道温度,并用于确定材料的热导率,验证器件热模型的准确性。建立模型时特别考虑了界面热阻的作用,确保器件温度分布的仿真结果与实验测量结果一致。文中采用包含界面热阻效应的三维热模型,系统的分析了栅指数目,器件栅宽和栅栅间距等因素对AlGaN/GaN 高电子迁移率晶体管热特性的影响。最后,提出了一种优化器件栅指间距的热设计方法,能够有效降低器件工作时的最高温度。     

X波段AlGaN/GaN HEMTs Γ栅场板结构研究

基于SiC衬底成功研制X波段0.25 μm栅长带有r栅场板结构的AlGaN/GaN HEMT,设计场板(field plate)长度为0.4 μm,0.6μm,0.7μm,0.9μm.研究了r栅场板长度及不同漏偏压下对器件直流,小信号特性及大信号的影响.器件直流I-V及转移特性并不依赖场板长度变化,增加场板长度器件击穿电压提高可达108 V,器件截止频率及振荡频率下降,输出功率大幅度提高,结合器件小信号提参结果分析.8 GHz下,总栅宽1 mm,场板长度为0.9 μm的器件,连续波输出功率密度7.11 W/mm,功率附加效率(PAE)35.31%,相应线性增益10.25 dB.     

基于AlGaN/GaN HEMT的C波段混合集成功率合成放大器的设计

研制了一种基于AlGaN/GaN HEMT的功率合成技术的混合集成放大器电路.该电路包含4个10×120 μm的HEMT晶体管以及一个Wilkinson功率合成器和分配器.在偏置条件为VDS=40V,IDS=0.9A时,输出连续波饱和功率在5.4GHz达到41.4dBm,最大的PAE为32.54%,并且功率合成效率达到69%.     

基于氟等离子体表面处理技术的AlGaN/GaN HEMT器件栅正向泄漏电流研究

The gate forward leakage current in AlGaN/GaN high electron mobility transistors(HEMTs) is investigated. It is shown that the current which originated from the forward biased Schottky-gate contributed to the gate forward leakage current.Therefore,a fluorine-plasma surface treatment is presented to induce the negative ions into the AlGaN layer which results in a higher metal-semiconductor barrier.Consequently,the gate forward leakage current shrinks.Experimental results confirm that the gate forward leakage current is decreased by one order magnitude lower than that of HEMT device without plasma treatment.In addition,the DC characteristics of the HEMT device with plasma treatment have been studied.     

Effect of the post-gate annealing on the gate reliability of AlGaN/GaN HEMTs

In this paper,we investigated the effect of post-gate annealing (PGA) on reverse gate leakage and the reverse bias reli-ability of Al0.23Ga0.77N/GaN high electron mobility transistors (HEMTs).We found that the Poole-Frenkel (PF) emission is domin-ant in the reverse gate leakage current at the low reverse bias region (Vth ＜ VG ＜ 0 V) for the unannealed and annealed HEMTs.The emission barrier height of HEMT is increased from 0.139 to 0.256 eV after the PGA process,which results in a reduction of the reverse leakage current by more than one order.Besides,the reverse step stress was conducted to study the gate reliabil-ity of both HEMTs.After the stress,the unannealed HEMT shows a higher reverse leakage current due to the permanent dam-age of the Schottky gate.In contrast,the annealed HEMT shows a little change in reverse leakage current.This indicates that the PGA can reduce the reverse gate leakage and improve the gate reliability.     

采用注入隔离制造的AlGaN/GaN HEMTs器件

对Al Ga N/Ga N HEMT器件采用离子注入技术注入氦离子进行隔离,应用该技术制造出的器件在室温下具有很好的特性.器件的阈值电压在- 3V左右时,源漏间电流为几十n A.肖特基势垒的反向漏电流在- 1 0 V下约为几百n A.与采用干法刻蚀技术进行隔离的器件相比,采用离子注入技术不但可以获得全平面化的HEMTs器件而且还有效地抑制了场区漏电.研究还表明氦离子注入的温度稳定性大于70 0℃.     

AlGaN/GaN HEMT欧姆接触的研究进展

从欧姆接触形成的机理出发,介绍了在AlGaN/GaN HEMT中实现源和漏区欧姆接触的各种方法,如表面处理技术、金属化系统和重掺杂技术等.回顾了近年来这些方法的研究进展.     

X波段AlGaN/GaN HEMTs厂栅场板结构研究

基于SiC衬底成功研制X波段0.25um栅长带有г栅场板结构的AlGaN/GaN HEMT,对比T型栅结构器件,研究了г栅场板引入对器件直流、小信号及微波功率特性的影响.结果表明,г栅场板结构减小器件截止频率及振荡频率,但明显改善器件膝点电压和输出功率密度.针对场板长度分别为0.4、0.7、0.9、1.1 um,得出一定范围内增加场板长度,器件输出功率大幅度提高,并结合器件小信号模型提参结果分析原因.在频率8 GHz下,总栅宽1 mm,场板长度0.9um的器件,连续波输出功率密度7.11 W/mm,功率附加效率(PAE)35.31%,相应线性增益10.25 dB.     

14W X波段AlGaN/GaN HEMT功率MMIC

报道了研制的SiC衬底AIGaN/GaN HEMT微带结构微波功率MMIC,芯片工艺采用凹槽栅场板结构提高AlGaN/GaNHEMTs的微波功率特性.S参数测试结果表明AlGaN/GaN HEMTs的频率特性随器件的工作电压变化显著.研制的该2级功率MMIC在9～11GHz带内30V工作,输出功率大于10W,功率增益大于12dB,带内峰值输出功率达到14.7W,功率增益为13.7dB,功率附加效率为23%,该芯片尺寸仅为2.0mm×1.1mm.与已发表的X波段AlGaN/GaN HEMT功率MMIC研制结果相比,本项工作在单位毫米栅宽输出功率和芯片单位面积输出功率方面具有优势.     

AlGaN/GaN共栅共源HEMTs器件

研究了蓝宝石衬底AlGaN／GaN共栅共源器件的特性。该器件包括栅长0．8μm共源器件与栅长1μm的共栅器件。研究表明,共栅共源器件的第二栅压对的器件饱和电流与跨导有明显的调制作用,容易实现功率增益控制。与共源器件相比,共栅共源器件在微波特性上fT大约9GHz,比共源器件稍小,但是具有较低的反馈,显著增加的功率资用增益及较高的端口阻抗,与共源器件相比,稳定性更好,可以避免振荡的产生,结合GaN的高功率特性GaN共栅共源器件非常适合微波频段宽频大功率领域的应用。     

蓝宝石衬底上AIGaN／GaN HEMT自热效应研究

建立了包含“自热效应”的AIGaN／GaN HEMT（高电子迁移率晶体管）直流I-V特性解析模型。从理论的角度分析了自热效应对AlGaN／GaN HEMT器件的影响，并同已有的实验结果进行了对比，符合较好。证明基于这种模型的理论分析适于AIGaN／GaN HEMT器件测试及应用的实际情况。     

多栅指AlGaN/GaN HEMT器件自热效应研究

Self-heating in multi-finger AlGaN/GaN high-electron-mobility transistors(HEMTs) is investigated by measurements and modeling of device junction temperature under steady-state operation.Measurements are carried out using micro-Raman scattering to obtain the detailed and accurate temperature distribution of the device.The device peak temperature corresponds to the high field region at the drain side of gate edge.The channel temperature of the device is modeled using a combined electro-thermal model considering 2DEG transport characteristics and the Joule heating power distribution.The results reveal excellent correlation to the micro-Raman measurements, validating our model for the design of better cooled structures.Furthermore,the influence of layout design on the channel temperature of multi-finger AlGaN/GaN HEMTs is studied using the proposed electro-thermal model, allowing for device optimization.     

蓝宝石衬底AlGaN/GaN共栅共源微波HEMTs器件

报道了蓝宝石衬底AlGaN/GaN共栅共源器件的制备与特性.该器件包括栅长为0.8μm共源器件与栅长为1μm的共栅器件.实验表明,共栅器件的第二栅压会显著影响器件饱和电流与跨导特性,从而控制功率增益.与共源器件相比,共栅共源器件表现出稍低的fT、较低的反馈、显著增加的功率资用增益及较高的端口阻抗.     

蓝宝石衬底AlGaN/GaN共栅共源微波HEMTs器件

报道了蓝宝石衬底AlGaN/GaN共栅共源器件的制备与特性.该器件包括栅长为0.8μm共源器件与栅长为1μm的共栅器件.实验表明,共栅器件的第二栅压会显著影响器件饱和电流与跨导特性,从而控制功率增益.与共源器件相比,共栅共源器件表现出稍低的 f T、较低的反馈、显著增加的功率资用增益及较高的端口阻抗.     

Effects of rapid thermal annealing on ohmic contact of AIGaN/GaN HEMTs

Ohmic contacts with Ti/Al/Ti/Au source and drain electrodes on A1GaN/GaN high electron mobility transistors （HEMTs） were fabricated and subjected to rapid thermal annealing （RTA） in flowing N2. The wafer was divided into 5 parts and three of them were annealed for 30 s at 700, 750, and 800 ℃, respectively, the others were annealed at 750 ℃ for 25 and 40 s. Due to the RTA, a change from Schottky contact to Ohmic contact has been obtained between the electrode layer and the A1GaN/GaN heterojunction layer. We have achieved a low specific contact resistance of 7.41 × 10-6Ω cm2 and contact resistance of 0.54 Ω.mm measured by transmission line mode （TLM）, and good surface morphology and edge acuity are also desirable by annealing at 750 ℃ for 30 s. The experiments also indicate that the performance of ohmic contact is first improved, then it reaches a peak, finally degrading with annealing temperature or annealing time rising.     

Impact of UV/ozone surface treatment on AIGaN/GaN HEMTs

Surface treatment plays an important role in the process of making high performance AlGaN/GaN HEMTs. A clean surface is critical for enhancing device performance and long-term reliability. By experimenting with different surface treatment methods, we find that using UV/ozone treatment significantly influences the electrical properties of Ohmic contacts and Schottky contacts. According to these experimental phenomena and Xray photoelectron spectroscopy surface analysis results, the effect of the UV/ozone treatment and the reason that it influences the Ohmic/Schottky contact characteristics of AlGaN/GaN HEMTs is investigated.     

碳致深能级引起的AlGaN/GaN HEMT电流崩塌现象

AlGaN/GaN HEMT良好的功率特性虽然被大量报导,但其电流崩塌现象仍是一个令人困扰的问题,作者通过实验证明了导致其电流崩塌的一个因素.两个AlGaN/GaN样片被分别放在纯氮气和掺碳的氮气气氛中快速退火,利用XPS证明了后者中的碳元素含量远远大于前者.比较二者的I-V特性曲线,可发现碳杂质的引入可使AlGaN/GaN HEMT电流崩塌程度大大增加.分析表明:由碳杂质引入导致的深能级使得负栅压下俘获沟道中的载流子在正栅压下不能立刻释放,从而引起AlGaN/GaN HEMT中的电流崩塌现象.     

基于AlGaN/GaN HEMT的C波段功率放大器混合集成电路的设计

我们设计研制了一个基于Al GaN/GaN HEMT大功率放大器的混合集成电路.这个电路包含了1个10×120μm的HEMT晶体管,以及输入和输出匹配电路.在偏置条件为Vds=40 V,Ids=0.26 A时,输出连续波饱和功率在5.4 GHz达到37 dBm(5 W),最大的PAE为35.6%.在偏置条件为Vds=30 V,Ids=0.22 A时输出连续波饱和功率在5.4 GHz达到36.4dBm(4.4 W),最大的PAE为42.7%.     

Improved temperature model of AlGaN/GaN HEMT and device characteristics at variant temperature

In this paper, an improved temperature model for AlGaN/GaN high electron mobility transistor (HEMT) is presented. Research is being conducted for a high-performance building block for high frequency applications that combine lower costs with improved performance and manufacturability. The effects of channel conductance in the saturation region and the parasitic resistance due to the undoped GaN buffer layer have been included. The effect of both spontaneous and piezoelectric polarization induced charges at the AlGaN/GaN heterointerface has been incorporated. The proposed model is used to determine the transfer characteristics, output current-voltage characteristics and small-signal microwave parameters of HEMTs. The investigated temperature range is from 100–600 K. The small signal microwave parameters have been evaluated to determine the unity current gain cut-off frequency (f _T ). High f _T (10–70 GHz) values and high current levels (～550 mA/mm) are achieved for a 1 μm AlGaN/GaN HEMTs. A custom DC measurement system is used to facilitate the DC characterization of the unpackaged GaN HEMT test device. The calculated critical parameters and the simulation results suggest that the performance of the proposed device degrades at elevated temperatures.