氮极性GaN/In0.17Al0.83N高电子迁移率晶体管材料机理与器件特性分析

晶格匹配的氮极性(N-polar)GaN/In0.17Al0.83N异质结以其优异的材料与电特性受到了研究者的广泛关注.通过自洽求解薛定谔方程和泊松方程,结合准二维模型,模拟计算了 N-polar GaN/In0.17Al0.83N高电子迁移率晶体管(HEMT)相关材料与器件特性.分析显示GaN沟道层、In0.17Al...     

混合极性GaN基HEMT中2DEG性能分析

综合镓极性(Ga-polar)和氮极性(N-polar)GaN基高电子迁移率晶体管(HEMT)上的欧姆接触特性,提出了一种混合极性的GaN基HEMT结构。通过自洽求解薛定谔方程和泊松方程,分析了该混合极性GaN基HEMT结构中的二维电子气(2DEG)行为特性,从而为该混合极性HEMT结构的实际应用提供了理论参考。仿真结果表明N-polar AlGaN背势垒的Al组分较其厚度对2DEG的影响更为明显,而将N-polar AlGaN背势垒的Al组分渐变后,可以降低寄生沟道对主沟道2DEG的影响,AlN插入层的引入也可进一步提高2DEG面密度、迁移率及其限阈性。     

Ti/Al/Ni/Au在N-polar GaN上的欧姆接触

N-polar GaN以其特有的材料特性和化学活性日益受到研究者关注,而N-polar GaN上欧姆接触也成为研究的热点。以Ti/Al/Ni/Au作为欧姆接触金属,分析了N-polar GaN上欧姆接触的最优退火条件,并借助剖面透射电子显微镜(TEM)和能量色散X射线能谱仪(EDX)研究了金属和N-polar GaN之间的反应生成物。结果表明,当退火温度升高到860℃时,可得到比接触电阻率ρc为1.7×10~(-5)Ω·cm~2的最优欧姆接触特性。TEM和EDX测试发现,除了生成已报道的AlN,还会在界面处产生多晶AlO_x,两者共同作用会进一步拉高势垒,从而对N-polar GaN上欧姆接触产生不利影响。     

我国利用氮化镓器件从事核应用研究取得系列成果

氮化镓(GaN)是一种III/V直接带隙半导体,作为第三代半导体材料的代表,随着其生长工艺的不断发展完善,现已广泛应用于光电器件领域,如激光器(LD)、发光二极管(LED)、高电子迁移率晶体管(HEMT)等。GaN基材料的良好抗辐射性能和环境稳定性,使得其在核探测领域具有很好的应用前景,在新型核电池领域也具有巨大的应用潜     

消息报道

苏州纳米所利用氮化镓器件从事核应用研究取得系列成果氮化镓(GaN)是一种III/V直接带隙半导体,作为第三代半导体材料的代表,随着其生长工艺的不断发展完善,现已广泛应用于光电器件领域,如激光器(LD)、发光二极管(LED)、高电子迁移率晶体管(HEMT)等。GaN基材料的良好抗辐射性能和环境稳定性,使得其在核探测领域具有很好的应用前景,在新型核电池领域也具有巨大的应用潜力。因为GaN辐生伏特效应核电池     

AlInN/GaN高电子迁移率晶体管的研究与进展

由于GaN基材料的高温性能好,AlInN/GaN异质界面具有更高的二维电子气密度,因而AlInN/GaN高电子迁移率晶体管(HEMT)具有更高的工作频率和饱和漏电流,以及更强的抗辐射能力,近年来成为微波功率器件和放大电路的研究热点。首先总结了AlInN材料的基本性质,分析了AlInN/GaNHEMT的材料生长和器件结构设计,最后总结了其在高频、大功率方面的最新进展。     

N-polar GaN上的欧姆接触:材料制备、金属化方案与机理

氮极性(N-polar)GaN与镓极性(Ga-polar)GaN极性相反,且具有较高的表面化学活性,使其在光电子、微电子及传感器等领域逐渐受到关注。文章结合一些相关研究报道,综述了N-polar GaN上欧姆接触的研究进展。首先对N-polar GaN材料的制备进行了分析,随后对N-polar GaN的欧姆接触电极的金属化方案及欧姆接触机理等内容进行了综合讨论,以期为实际N-polar GaN欧姆接触研究提供一些参考。     

AlGaN/GaN HEMT氢气传感器不同温度下响应特性的研究

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V_(GS)=-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。     

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。     

集成电子薄膜材料研究进展

首先分析了当前我国电子信息产业的现状,特别是电子材料与元器件行业的状况,结合国际上电子信息技术的发展趋势,阐述了研究集成电子材料的重要意义.文章结合作者的工作主要介绍了介电/GaN集成电子薄膜生长控制与性能研究情况,采用TiO2(诱导层)/MgO(阻挡层)组合缓冲层的方法控制介电/GaN集成薄膜生长取向、界面扩散,保护GaN基半导体材料的性能,降低介电/GaN集成薄膜界面态密度,建立界面可控的相容性生长方法.通过集成结构的设计与加工,研制出介电增强型GaN HEMT器件、高耐压GaN功率器件原型以及一体化集成的微波电容、变容管、压控振荡器、混频器等新型元器件.     

Multilayer AIN/AlGaN/GaN/AlGaN heterostructures with quantum wells for high-power field-effect transistors grown by ammonia MBE

High-power field-effect transistors (FETs) are among the main applications of heterostructures based on group III metal nitrides, which in most cases implement the classical GaN/AlGaN structure with a single junction. An alternative approach based on the use of double heterostructures with imporved two-dimensional electron gas (2DEG) confinement offers a number of advantages, but such structures are usually characterized by a lower carrier mobility and density (in GaN layers of reduced thickness) as compared to the values in the single-junction structures. Optimization of the heterostructure design and ammonia MBE growth conditions allowed us to obtain multilayer AlN/AlGaN/GaN/AlGaN heterostructures with quantum wells, which are characterized by a 2DEG carrier mobility of 1100–1300 cm²/(V s) and a sheet electron density of (1.1–1.3) × 10¹³ cm^-2. Experimental FETs based on the obtained multilayer heterostructures in a static regime exhibit working current densities up to 0.6 A/mm at a transconductance of up to 150 mS/mm and a breakdown voltage above 100 V.     

Thermal stability of N-polar n-type Ohmic contact for GaN-based light emitting diode on Si substrate

Thermal stability of N-polar n-type Ohmic contact for GaN light emitting diode (LED) on Si substrate was investigated. Al/Ti/Au were deposited as the contacts on the N-polar n-type GaN with and without AlN buffer layer on the surface, respectively, and both contacts exhibited Ohmic behaviors. The samples with AlN showed excellent Ohmic contact thermal stability when annealed below 700 °C, while the samples without AlN experienced serious degradation on electrical properties after being annealed in the temperature range of 250-600 °C. After the process of aging at 30 mA (155 A/cm²) and room temperature for 1000 h, operating voltage increase less than 0.05 V for LEDs with AlN but more than 0.45 V for LEDs without AlN. Therefore, we conclude that the existence of AlN buffer layer is a key of forming high stable Ohmic contact for GaN-based vertical structure LED on Si substrate.     

GaN-based FETs using Cat-CVD SiN passivation for millimeter-wave applications

We have found that SiN passivation by catalytic chemical vapor deposition (Cat-CVD) can significantly increase an electron density of an AlGaN/GaN heterostructure field-effect transistor (HFET). This effect enables thin-barrier HFET structures to have a high-density two-dimensional electron gas and leads to suppression of short-channel effects. We fabricated 30-nm-gate Al_0.4Ga_0.6N(8 nm)/GaN HFETs using Cat-CVD SiN. The maximum drain current density and extrinsic transconductance were 1.49 A/mm and 402 mS/mm, respectively. Current-gain cutoff frequency and maximum oscillation frequency of the HFETs were 181 and 186 GHz, respectively. These high-frequency device characteristics are sufficiently high enough for millimeter-wave applications.     

Normally off transistors based on in situ passivated AlN/GaN heterostructures

A molecular beam epitaxy technology of in situ passivated SiN/AlN/GaN heterostructures with an ultrathin AlN barrier has been developed. Based on these structures, normally off transistors with maximum current density of about 1 A/mm, saturation voltage of about 1 V, transconductance up to 350 mS/mm, and breakdown voltage above 60 V have been fabricated, in which the drain and gate current collapse phenomena are virtually absent.

     

Investigation of the interface properties of MOVPE grown AlGaN/GaN high electron mobility transistor (HEMT) structures on sapphire

We have developed a virtual GaN substrate on sapphire based on a two-step growth method. By optimizing the growth scheme for the virtual substrate we have improved crystal quality and reduced interface roughness. Our Al_0.22Ga_0.78N/GaN HEMT structure grown on the optimized semi-insulating GaN virtual substrate, exhibits Hall mobilities as high as 1720 and 7350 cm²/Vs and sheet carrier concentrations of 8.4 × 1012 and 10.0 × 1012 cm^− 2 at 300 K and 20 K, respectively. The presence of good AlGaN/GaN interface quality and surface morphology is also substantiated by X-Ray reflectivity and Atomic Force Microscopy measurements. A simplified transport model is used to fit the experimental Hall mobility.     

Multilayer AlN/AlGaN/GaN/AlGaN heterostructures for high-power field-effect transistors grown by ammonia MBE

The results of the optimization of the ammonia MBE technology of AlN/AlGaN/GaN/AlGaN heterostructures for high-power microwave field-effect transistors (FETs) are presented. The creation of technological systems of the EPN type for the deposition of group III nitrides by ammonia MBE, in combination with the development of optimum growth and postgrowth processes, make it possible to obtain AlN/AlGaN/GaN/AlGaN based heterostructures for high-power microwave FETs with the output static characteristics on the world best level. One of the main fields of application of the semiconductor heterostructures based on group III nitrides is the technology of high electron mobility transistors (HEMTs). Most investigations in this field have been devoted to the classical GaN/AlGaN structures with a single heterojunction. An alternative approach based on the use of double heterostructures with improved two-dimensional electron gas (2DEG) confinement offers a number of advantages, but such structures are usually characterized by a lower carrier mobility as compared to that in the single-junction structures. We succeeded in optimizing the double heterostructure parameters and growth conditions so as to obtain conducting channels with a 2DEG carrier mobility of 1450, 1350, and 1000 cm²/(V s) and a sheet electron density of 1.3 × 10¹³, 1.6 × 10¹³, and 2.0 × 10¹³ cm^?2, respectively. Experimental HEMTs with 1-μm-long gates based on the obtained multilayer heterostructure with a doped upper barrier layer exhibit stable current-voltage characteristics with maximum saturation current densities of about 1 A/mm and a transconductance of up to 180 mS/mm.     

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.     

Heteroepitaxial growth of III–V compound semiconductors for optoelectronic devices

An AlGaAs/GaAs multi-quantum well vertical-cavity surface-emitting laser diode (VCSELD) has been grown on a Si substrate using metalorganic chemical vapour deposition (MOCVD). The VCSELD with a 23-pair of AlAs/Al_0·1Ga_0·9As distributed Bragg reflector on a Si substrate exhibited a threshold current of 223 mA under continuous-wave condition at 220 K. Electroluminescence observation showed that an optical degradation was caused by generation and growth of dark-line defects. An MOCVD-grown InGaN/AlGaN double-heterostructure light-emitting diode on a sapphire substrate exhibited an optical output power of 0·17 mW, an external quantum efficiency of 0·2%, a peak emission wavelength at 440 nm with a full width at half-maximum of 63 nm and a stable operation up to 3000 h under 30 mA DC operation at 30°C. A high current level of 281 mA/mm and a large transconductance (g _m) of 33 mS/mm have been achieved for a GaN metal semiconductor field-effect transistor (MESFET) with a gate length of 2 μm and a width of 200 μm at 25°C. The GaN MESFET at 400°C showed degraded characteristics: a lowg _m of 13·4 mS/mm, a gate leakage and a poor pinch-off.     

Comparison of wurtzite and zinc blende III–V nitrides field effect transistors: a 2D Monte Carlo device simulation

An ensemble Monte Carlo method is used to compare the potentialities of zinc blende and wurtzite GaN for field effect transistor applications. First, bulk material electron transport properties are compared and we find that mobility, steady state velocity and velocity overshoot are at the advantage of zinc blende GaN. Then, zinc blende GaN and wurtzite GaN MESFET with very short gate length (L_g=0.12 μm) are investigated using a 2D Monte Carlo device simulation. A 50% gain in performance is obtained for the zinc blende GaN MESFET as compared with the wurtzite one. A zinc blende AlGaN/GaN HEMT is also simulated and exhibits a current density of 900 mA mm⁻¹, a transconductance of 480 mS mm⁻¹ and a cut-off frequency of 180 GHz.