AlGaN/GaN HEMT氢气传感器不同温度下响应特性的研究北大核心CSCD

本文制作了栅极为金属Pt的AlGaN/GaN HEMT结构的氢气传感器。当外加偏压VGS=-2.5 V时,研究了传感器在不同温度(25-150℃)下对不同氢气浓度(25-900 ppm)的响应特性。研究结果表明:当温度为25℃、氢气浓度为25 ppm时,器件响应的灵敏度为65.9%;随着氢气浓度从25增加到900 ppm后,器件灵敏度增加了14%,器件灵敏度与浓度的对数呈线性关系。当温度在25-150℃的区间内,传感器响应的灵敏度随着温度升高而降低,在室温25℃时其响应最佳。此外,通过修正Langmuir吸附等温线建立了传感器响应的理论模型,将实验数据通过理论模型进行拟合,分析了温度对传感器响应的影响。本工作研究的氢气传感器具有优异的响应特性,它可应用于室温氢气检测,具有极高的应用潜力。     

栅源双场板对GaNHEMT器件性能的影响

本文对具有不同的栅源双场板结构的p-GaN栅HEMT器件的性能进行了比较,利用半导体器件仿真工具Synopsys TCAD对器件电学特性进行了分析。仿真结果显示:栅源复合场板结构能改善栅场板边缘的电场峰值,在源极场板边缘产生一个新的峰值,可使器件的击穿电压提高到1365V;间断栅场板与源场板复合结构,能在场板间隙位置产生新的电场峰值,更充分的利用漂移区耐压,使其击穿电压值达到1478V;栅源复合间断场板结构能缓解源场板对栅间断处电场峰值的抑制作用,器件击穿电压提高到最大值1546V。     

基于AlGaN/GaN HEMT结构的氢气传感器

制作了栅极修饰金属Pt的AlGaN/GaN高电子迁移率晶体管结构的氢气传感器.栅极Pt采用溅射的方法制作,主要起到形成肖特基接触并催化氢气裂解的作用.器件的栅极敏感区域尺寸为5 μm×400μm,对常温下氢气浓度为2× 10-6至6216× 10-6的氢气/氮气混合气进行了检测.结果表明,在VGs=-1.5V,VDS=1 V的工作偏压下,10倍的氢气浓度变化平均引起33.9％的灵敏度变化量.同时,器件对2× 10-6的氢气具有6.3％的灵敏度,表现出了具有竞争力的低浓度检测极限.     

AlGaN／GaN异质结2DEG载流子输运

本言语采用雷－丁平衡方程理论,考虑杂质散射、声学波形变势散射、声学波压电散射、极化光学波散射等散射机制,计算了ＡｌＧａＮ／ＧａＮ异质结二维电子气（２ＤＥＧ）在０－３００Ｋ温度范围内的低场迁率以及电子漂移速度和电子温度随外加电场的变化关系,同时本文计算了有隔离层的调制掺杂异质结构（ＭＤＨ）中低温下（Ｔ＝４Ｋ）低场迁移率随隔离层厚度的变化关系。计算结果表明在低温下ＡｌＧａＮ／ＧａＮ异质结构的低场迁移率     

改进的AlGaN/GaN HEMT小信号参数提取算法

制作了截止频率ft和最高震荡频率fmax分别为46.2和107.8 GHz的AlGaN/GaN高电子迁移率晶体管,并针对该器件建立了包含微分电阻Rfd和Rfs在内的18元件小信号等效电路模型;在传统的冷场条件提取器件寄生参数的基础上,通过对不同栅压偏置下冷场Z参数进行线性插值运算,可消除沟道分布电阻和栅极泄漏电流对寄生电阻的影响;再利用热场S参数对寄生参数部分进行去嵌,可提取得到本征参数。分析表明,此模型和算法提高了模型拟合精度,S参数的仿真结果与测试数据在200MHz到40GHz的频率范围内均符合很好,误差不到2%。     

AlN钝化层对AlGaN/GaN异质结及其高温特性的影响

主要研究了A1N钝化介质层对AlGaN/GaN异质结势垒层应力的修改以及应力的变化对二维电子气高温输运性质的影响.研究结果表明:AlN介质层会对AlGaN势垒层产生附加的平面压应变;AlN和传统的si3N4钝化介质都能减轻AlGaN势垒层在高温下的应变弛豫,但AlN介质层效果更明显.和传统的Si,N4钝化介质相比较,AlN钝化层不仅会显著增加AlGaN/GaN异质结二维电子气密度度,还会明显提高二维电子气迁移率,同时,AlN钝化后二维电子气密度的温度稳定性也更好.因此,对AlGaN/GaN异质结器件来说,AIN是一种有潜力的钝化介质.     

RF-MBE生长AlGaN/GaN二维电子气材料

用射频等离子体辅助分子束外延技术 (RF -MBE)在C面蓝宝石衬底上外延了高质量的GaN膜以及AlGaN/GaN极化感应二维电子气材料 .所外延的GaN膜室温背景电子浓度为 2× 10 17cm-3 ,相应的电子迁移率为 177cm2 /Vs;GaN (0 0 0 2 )X射线衍射摇摆曲线半高宽 (FWHM)为 6arcmin .;AlGaN/GaN极化感应二维电子气材料的室温电子迁移率为 730cm2 /Vs ,相应的电子气面密度为 7.6× 10 12 cm-2 ;用此二维电子气材料制作的异质结场效应晶体管 (HFET)室温跨导达 5 0mS/mm (栅长 1微米 ) ,截止频率达 13 .2 5GHz(栅长 0 .5微米 ) ,可在 30 0℃下工作     

AlGaN基UV-LED的研究与进展

近年来短波长紫外LED巨大的应用价值引起了人们的高度关注,成为了全球半导体领域研究和投资的新热点。本文综合分析了AlGaN材料的生长、碎裂、掺杂和欧姆接触等问题,对UV—LED的发展历程、技术路线和研究进展进行了详细介绍,并展望了未来发展方向。     

氧气等离子体处理对AlGaN肖特基接触的影响

研究了不同的干法刻蚀以及氧气等离子体处理条件对AlGaN表面特性的影响。在合适的条件下,氧气等离子体处理可以使AlGaN表面发生氧化,并使肖特基接触的反向漏电流降低两个数量级,反向击穿电压也有显著提高。该方法简单易行,可应用于制备高性能的AlGaN／GaN HEMT器件。     

AlGaN外延薄膜材料的椭圆偏振光谱研究

对蓝宝石衬底上生长的一系列AlxGa1-xN薄膜进行了椭圆偏振光谱研究,得到了薄膜的厚度以及245～1000nm的光学常数;通过有效介质模型计算出Al组分;随着Al组分的增加,折射率n下降,吸收边蓝移,与透射光谱结果一致。     

AlGaN/GaN HEMT栅槽低损伤刻蚀技术

对AlGaN/GaN HEMT栅槽低损伤刻蚀技术进行研究,通过加入小流量的具有钝化缓冲作用的C2H4,对Cl2/Ar/C2H4的工艺条件进行了优化,有效地降低了栅槽刻蚀造成的AlGaN表面损伤和器件退化,同时防止反应生成物淀积在栅槽表面,改善了肖特基结特性,提高了栅极调控能力,实现凹栅槽的低损伤刻蚀.     

AlGaN/GaN HEMTs passivated by Cat-CVD SiN Film

We demonstrate the excellent performance of a 140 W AlGaN/GaN HEMT in the C-band, which is passivated by a Cat-CVD SiN film. The interface trap density of the AlGaN surface passivated by Cat-CVD film after NH₃ treatment is 3 × 10¹² cm^− 2, which is the smallest of investigated deposition techniques. The lowest interface trap density achieved by the Cat-CVD technique makes it possible to operate the AlGaN/GaN HEMT in the C-band. We clarify that the Cat-CVD technique is necessary for developing future amplifiers.     

Suitability of thin-GaN for AlGaN/GaN HEMT material and device

Journal of Materials Science - In this study, we report about the suitability of thin-GaN (~ 200 nm) for AlGaN/GaN HEMT (High Electron Mobility Transistor) material and device....     

考虑自热效应的AlGaN/GaN高电子迁移率晶体管建模与仿真

基于电荷控制模型,分析了极化,载流子迁移率,饱和电子漂移速度,导带断续,掺杂浓度,沟道温度等与自然效应的关系,并考虑了寄生电阻对自热效应的影响,建立了模拟AlGaN/GaN高电子迁移率晶体管直流I-V特性的解析模型。通过与试验值的对比,该模型具有较高的精度,并且计算过程简单,可以用来指导器件结构和电路的设计。     

Low-Energy Defectless Dry Etching of the AlGaN/AlN/GaN HEMT Barrier Layer

A method of defectless dry etching of an AlGaN barrier layer is proposed, which consists in repeated plasmachemical oxidation of AlGaN and removal of the oxide layer by means of reactive ion etching in inductively coupled BCl₃ plasma. Using the proposed etching technology, AlGaN/AlN/GaN high-electron-mobility transistors (HEMTs) with a buried gate have been successfully fabricated for the first time. It is shown that the currents of obtained HEMTs are independent of the number of etching cycles, while the gate operating point shifts toward positive voltages up to obtaining transistors operating in the enhancement mode.     

Impact of SF6 plasma treatment on performance of AlGaN/GaN HEMT

Selective plasma treatment of an AlGaN/GaN heterostructure in the RF discharge of the electronegative SF₆ gas was studied. Shallow recess-gate etching of AlGaN (∼5 nm) was performed in CCl₄ plasma through a photoresist mask. Subsequently, recess-gate etching followed in situ by SF₆ plasma. The plasma treatment provides the following advantages in the technology of AlGaN/GaN high-electron mobility transistors (HEMT): It (1) simplifies their technology; (2) ensures sufficient selectivity; and (3) enables the technologist to set the threshold voltage of the HEMTs controllably. At the same time, the treatment can (1) provide the AlGaN/GaN heterostructure with surface passivation; (2) modify the 2DEG in any area of a HEMT channel; and (3) make it possible to convert a HEMT operation from depletion mode to enhancement mode. The treatment also improved significantly the DC and RF parameters of HEMTs studied.     

Improved DC performance of AlGaN/GaN high electron mobility transistors using hafnium oxide for surface passivation

Improved DC performance of AlGaN/GaN high electron mobility transistors (HEMTs) have been demonstrated using reactive-sputtered hafnium oxide (HfO₂) thin film as the surface passivation layer. Hall data indicate a significant increase in the product of sheet carrier concentration (n_s) and electron mobility (μ_n) in the HfO₂-passivated HEMTs, compared to the unpassivated HEMTs. This improvement in electron carrier characteristics gives rise to a 22% higher I_Dmax and an 18% higher g_mmax in HEMTs with HfO₂ passivation relative to the unpassivated devices. On the other hand, I_gleak of the HEMTs decreases by nearly one order of magnitude when HfO₂ passivation is applied. In addition, drain current is measured in the subthreshold regime. Compared to the unpassivated HEMTs, HfO₂-passivated HEMTs exhibit a much smaller off-state I_D, indicating better turn-off characteristics.     

Irradiation effects on AlGaN HFET devices and GaN layers

AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with protons as well as carbon, oxygen, iron and krypton ions of high (68 and 120 MeV) and low (2 MeV) energy with fluences in the range from 1 × 10⁷ to 1 × 10¹³ cm^?2. High energy irradiation with protons, carbon and oxygen produced no degradation in devices while krypton irradiation at the fluence of 1 × 10¹⁰ cm^?2 resulted in a small reduction of 2% in the transconductance. Similarly, for GaN samples irradiated with protons, carbon and oxygen at high energy no changes were seen by XRD, PL and Hall effect, while changes in lattice constant and a reduction in PL intensity were observed after irradiation with high energy krypton. Low energy irradiation with carbon and oxygen at a fluence of 5 × 10¹⁰ cm^?2 results in small change in the device performance while remarkable changes in device characteristics are seen at a fluence of 1 × 10¹² cm^?2 for carbon, oxygen, iron and krypton irradiation. Similarly changes are also observed by XRD, PL and Hall effect for the thick GaN layer irradiated at the fluence of 1 × 10¹² cm^?2. The device results and GaN layer properties are strongly correlated.     

Surface acoustic wave excitation on SF6 plasma-treated AlGaN/GaN heterostructure

In this work, we introduce a new modified approach to the formation of interdigital transducer (IDT) structures on an AlGaN/GaN heterostructure. The approach is based on a shallow recess-gate plasma etching of the AlGaN barrier layer in combination with “in-situ” SF₆ surface plasma treatment applied selectively under the Schottky gate fingers of IDTs. It enables one to modify the two-dimensional electron gas (2DEG) density and the surface field distribution in the region of the IDTs, as is needed for the excitation of a surface acoustic wave (SAW). The measured transfer characteristics of the plasma-treated SAW structures revealed the excitation of SAW at zero bias voltage due to fully depleted 2DEG in the region of the IDTs. High external bias voltages are not necessary for SAW excitation. SIMS depth distribution profiles of F atoms were measured to discuss the impact of SF₆ plasma treatment on the performance of the AlGaN/GaN-based IDTs.     

Analysis of the thermal behavior of AlGaN/GaN HEMTs

The thermal behavior of state-of-the-art multifinger AlGaN/GaN HEMTs grown on SiC is thoroughly analyzed under steady-state and dynamic conditions. Accurate 3-D FEM simulations – based on a novel in-house tool devised to automatically build the device mesh – are performed using a commercial software to explore the influence of various layout and technological solutions on the temperature field. An in-house routine is employed to determine the Foster/Cauer networks suited to describe the dynamic heat propagation through the device structure. To conclude, various experimental techniques are employed to assess the thermal resistance and to allow the monitoring of the thermal impedance versus time of the transistors under test.