High-efficiency S-band harmonic tuning GaN amplifier

In this paper, we present a high-efficiency S-band gallium nitride （GaN） power amplifier （PA）. This amplifier is fabri- cated based on a self-developed GaN high-electron-mobility transistor （HEMT） with 10 mm gate width on SiC substrate. Harmonic manipulation circuits are presented in the amplifier. The matching networks consist of microstrip lines and discrete components. Open-circuited stub lines in both input and output are used to tune the 2rid harmonic wave and match the GaN HEMT to the highest efficiency condition. The developed amplifier delivers an output power of 48.5 dBm （70 W） with a power-added efficiency （PAE） of 72.2% at 2 GHz in pulse condition. When operating at 1.8-2.2 GHz （20% relative bandwidth）, the amplifier provides an output power higher than 48 dBm （,-~ 65 W）, with a PAE over 70% and a power gain above 15 dB. When operating in continuous-wave （CW） operating conditions, the amplifier gives an output power over 46 dBm （40 W） with PAE beyond 60% over the whole operation frequency range.     

100-nm T-gate InAIAs/InGaAs InP-based HEMTs with fT= 249 GHz and fmax ： 415 GHz

InA1As/InGaAs high electron mobility transistors （HEMTs） on an InP substrate with well-balanced cutoff frequency fT and maximum oscillation frequency frnax are reported. An InA1As/InGaAs HEMT with 100-nm gate length and gate width of 2 × 50 μm shows excellent DC characteristics, including full channel current of 724 mA/mm, extrinsic maximum transconductance gm.max of 1051 mS/mm, and drain-gate breakdown voltage BVDG of 5.92 V. In addition, this device exhibits fT = 249 GHz and fmax = 415 GHz. These results were obtained by fabricating an asymmetrically recessed gate and minimizing the parasitic resistances. The specific Ohmic contact resistance was reduced to 0.031 0.mm. Moreover, the fT obtained in this work is the highest ever reported in 100-nm gate length InA1As/InGaAs InP-based HEMTs. The outstanding gm.max, fT, fmax, and good BVDG make the device suitable for applications in low noise amplifiers, power amplifiers, and high speed circuits.     

Non-recessed-gate quasi-E-mode double heterojunction AIGaN/GaN high electron mobility transistor with high breakdown voltage

A non-recessed-gate quasi-E-mode double heterojunction A1GaN/GaN high electron mobility transistor （quasi-E- DHEMT） with a thin barrier, high breakdown voltage and good performance of drain induced barrier lowering （DIBL） was presented. Due to the metal organic chemical vapor deposition （MOCVD） grown 9-nm undoped A1GaN barrier, the effect that the gate metal depleted the two-dimensiomal electron gas （2DEG） was greatly impressed. Therefore, the density of carriers in the channel was nearly zero. Hence, the threshold voltage was above 0 V. Quasi-E-DHEMT with 4.1%tm source-to-drain distance, 2.6-μm gate-to-drain distance, and 0.5-μm gate length showed a drain current of 260 mA/mm. The threshold voltage of this device was 0.165 V when the drain voltage was 10 V and the DIBL was 5.26 mV/V. The quasi-E-DHEMT drain leakage current at a drain voltage of 146 V and a gate voltage of -6 V was below 1 mA/mm. This indicated that the hard breakdown voltage was more than 146 V.     

第一性原理的形变势理论研究声学声子散射对电荷传输的影响

本文应用密度泛函理论和玻尔兹曼方程,在形变势理论的框架和驰豫时间近似下,研究了分子晶体中电子与声学声子散射对电荷传输的影响.针对蒽、萘、丁省和并五苯的计算表明,非局域化电子的传输过程主要受到来自于声学声子的散射.对于蒽晶体,与以前的Holstein-Peierls模型计算结果相比,发现纵向声学声子对空穴的散射强度是光学声子的3倍,所得到的空穴迁移率更接近超纯单晶样品的实验测量结果.同时,我们发现电子的本征迁移率比空穴还要大,应用前线轨道交叠分析可以合理地解释这一结果.     

利用空间电荷限制电流方法确定三(8-羟基喹啉)铝的电子迁移率特性初步研究

材料的迁移率是其关键电学特性之一.有机材料迁移率的研究对于有机电致发光器件、 有机太阳电池、有机薄膜场效应晶体管性能的提高有重要的意义. 应用简单易行的空间电荷限制电流方法,对基于三(8-羟基喹啉)铝(Alq₃) 的四种单载流子器件电流密度-电压曲线特性进行研究, 根据空间电荷限制电流模型,拟合出Alq₃材料在四种器件中的零场电子迁移率和电场依赖因子,并且给出Alq₃电子迁移率随外加偏压的变化趋势. 实验结果表明,顶电极铝蒸镀到缓冲层氟化锂(1 nm)和Alq₃ (100 nm)的表面后, 可以明显改善Alq₃的零场迁移率和电场依赖因子. 认为产生这种现象的原因是氟化锂可以使铝和Alq₃发生络合反应, 形成Li⁺¹Alq^-1粒子,形成良好的欧姆接触,使得电子的注入效率大大提高.     

一种基于碘化铅的有机/无机杂化钙钛矿材料传输性能的研究

合成了一种新型的有机/无机杂化钙钛矿(NH3C6H4OC6H4NH3)PbI4, 采用元素分析、紫外-可见光吸收光谱、X射线衍射和透射电镜对其结构进行了表征, 结果表明这种材料具有规则的层状结构, 有序性高. 对这种材料的薄膜进行了伏安测试, 结果表明该材料属于n型半导体, 其电子迁移率达到0.065 cm2•V－1•s－1, 在光电器件领域有着潜在的应用前景.     

AlN/β-Ga2O3异质结电子输运机制

β-Ga₂O₃具有禁带宽度大、击穿电场强的优点,在射频及功率器件领域具有广阔的应用前景.β-Ga₂O₃(201)晶面和AlN(0002)晶面较小的晶格失配和较大的导带阶表明二者具有结合为异质结并形成二维电子气(twodimensional electron gas,2DEG)的理论基础,引起了众多研究者关注.本文利用AlN的表面态假设,通过求解薛定谔-泊松方程组计算了AlN/β-Ga₂O₃异质结导带形状和2DEG面密度,并将结果应用于玻尔兹曼输运理论,计算了离化杂质散射、界面粗糙散射、声学形变势散射、极性光学声子散射等主要散射机制限制的迁移率,评估了不同散射机制的相对重要性.结果表明,2DEG面密度随AlN厚度的增加而增加,当AlN厚度为6 nm,2DEG面密度可达1.0×10¹³ cm^-2,室温迁移率为368.6 cm²/(V.s).在T<184 K的中低温区域,界面粗糙散射是限制2...