低开启电压的InGaP/GaAsSb/GaAs双异质结晶体管

采用窄禁带宽度材料GaAsSb作为异质结晶体管的基区材料 ,成功研制出了能有效降低电路工作电压和功率损耗的低开启电压的NPNInGaP/GaAsSb/GaAs双异质结晶体管 (doubleheterojunctionbipolartransistor,DHBT) .器件性能如下 :BE结的正向开启电压 (turn onvoltage)仅为 0 73V ;当IB=1μA/step时 ,直流增益达到了 10 0 ,BVCEO=5～ 6V .通过对基区不同Sb含量器件的比较得到 ,器件的直流特性与基区Sb的含量有关.     

发射区底切对倒置结构InP/GaAsSb/InP DHBT性能的影响

基于考虑载流子弹道输运等非局域传输瞬态效应的流体动力学模型,数值模拟计算了集电区在上面发射区在下面的倒置InP/GaAsSb/InP双异质结双极晶体管(DHBT)器件的直流输出特性和高频性能.计算结果表明:由于集电区台面面积小,集电区在上的倒置InP/GaAsSb/InP双异质结双极晶体管有较高的高频性能;对于发射区在下面与基区接触面积大导致较多的基区载流子复合而使器件的增益偏低问题,可以考虑掩埋侧边腐蚀工艺底切发射区的技术来减少发射区和基区的接触面积,从而减少复合改善器件的增益特性.     

基于MBE生长的一种Be掺杂InGaAs基区的新结构InGaP/InGaAs/GaAs DHBT

报道了一种以InGaAs为基区的新结构InGaP/InGaAs/GaAs双异质结晶体管,获得了直流性能良好的器件.其共射直流增益β达到100,残余电压Voffset约为0.4V,膝点电压Vknee约为1V,击穿电压BVceo超过10V,器件的基极和集电极电流理想因子分别为nb=1.16,nc=1.11,可应用于低功耗、高功率领域.     

基于MBE生长的一种Be掺杂InGaAs基区的新结构InGaP/InGaAs/GaAs DHBT

报道了一种以InGaAs为基区的新结构InGaP/InGaAs/GaAs双异质结晶体管,获得了直流性能良好的器件.其共射直流增益β达到100,残余电压Voffset约为0.4V,膝点电压Vknee约为1V,击穿电压BVceo超过10V,器件的基极和集电极电流理想因子分别为nb=1.16,nc=1.11,可应用于低功耗、高功率领域.     

基区As组分缓变对InP/InGaP/GaAsSb/InP DHBT热电性能的影响

基于非等温能量平衡传输模型,利用SILVACO/ATLAS数值计算软件,研究了四种不同基区As组分的缓变对InP/InGaP/GaAsSb/InP双异质结双极晶体管(DHBT)热电特性的影响。结果表明,As组分缓变的引入改善了器件的直流增益和特征频率,但同时器件内部温度也随之升高。直流增益和温度增加的速率随As组分缓变范围增大而增大,特征频率增加的速率随As组分缓变范围的增加而迅速减小。基区As组分为0.57至0.45由发射区侧到集电区侧线性分布的器件具有较高的增益和特征频率及较低的器件内部温度,增益、特征频率与器件内部温度得到了优化。     

新结构InGaP/GaAs/InGaP DHBT生长及特性研究

设计并生长了一种新的InGaP/GaAs/InGaP DHBT结构材料,采用在基区和集电区之间插入n+-InGaP插入层结构,以解决InGaP/GaAs/InGaP DHBT集电结导带尖峰的电子阻挡效应问题。采用气态源分子束外延(GSMBE)技术,通过优化生长条件,获得了高质量外延材料,成功地生长出带有n+-InGaP插入层结构的GaAs基InGaP/GaAs/InGaP DHBT结构材料。采用常规的湿法腐蚀工艺,研制出发射极面积为100μm×100μm的新型结构InGaP/GaAs/InGaP DHBT器件。直流特性测试的结果表明,所设计的集电结带有n+-InGaP插入层的InGaP/GaAs/InGaP DHBT器件开启电压约为0.15V,反向击穿电压达到16V,与传统的单异质结InGaP/GaAs HBT相比,反向击穿电压提高了一倍,能够满足低损耗、较高功率器件与电路制作的要求。     

InP/InGaP/GaAsSb/InGaAsSb/InP双异质结双极晶体管设计北大核心

应用半导体器件的电阻电容计算理论和SILVACO ATLAS软件,在综合考虑载流子渡越时间和电阻电容延迟时间对增益截止频率的影响下设计了一种InP/InGaP/GaAsSb/InGaAsSb/InP双异质结双极晶体管(DHBT)结构。该结构中在基区与发射区之间加入P型半导体层以降低基区与发射区之间的电子势垒,并通过引入梯度渐变材料及优化掺杂分布提高基区电场、增强集电区中易趋近于零区域的电场,器件的电流增益截止频率得到显著提升。此外,还列出了InGaP和InGaAsSb材料的禁带宽度和电子亲合势、P型GaAs_(0.51)Sb_(0.49)和InGaAsSb材料的电子迁移率的近似计算公式。     

SiGe HBT基区结构的优化对欧拉电压的影响

欧拉电压是SiGe HBT一项重要的直流参数,受到基区结构(如Ge组分)的影响。研究发现,高温过程会导致硼的外扩散,从而影响异质结的位置,使欧拉电压受到影响。实验发现,通过优化基区结构,加厚CB结处i-SiGe厚度,可获得VA=520 V,βVA=164,320 V的SiGe HBT。     

npn AlGaN/GaN HBT模型与特性分析

基于实验数据对GaN材料的少子寿命和碰撞电离率进行了建模,应用漂移-扩散传输模型开展了npnAlGaN/GaN异质结双极晶体管的特性研究,给出了器件导通电压、偏移电压和饱和电压的解析式.结果表明:实际器件导通电压、偏移电压及饱和电压较大的原因主要是高基区电阻和基区接触的非欧姆特性,为器件的工艺制造提供了理论指导.     

npn AlGaN/GaN HBT模型与特性分析

基于实验数据对GaN材料的少子寿命和碰撞电离率进行了建模,应用漂移-扩散传输模型开展了npnAlGaN/GaN异质结双极晶体管的特性研究,给出了器件导通电压、偏移电压和饱和电压的解析式.结果表明:实际器件导通电压、偏移电压及饱和电压较大的原因主要是高基区电阻和基区接触的非欧姆特性,为器件的工艺制造提供了理论指导.     

Performance improvement in tensile-strained In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As metamorphic HEMT

This paper proposes a In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As (x=0.3-0.5-0.3) metamorphic high-electron mobility transistor with tensile-strained channel. The tensile-strained channel structure exhibits significant improvements in dc and RF characteristics, including extrinsic transconductance, current driving capability, thermal stability, unity-gain cutoff frequency, maximum oscillation frequency, output power, power gain, and power added efficiency.     

Very low-noise Al/sub 0.3/Ga/sub 0.7/As/Ga/sub 0.65/In/sub 0.35/As/GaAs single quantum-well pseudomorphic HEMTs

AlGaAs/GaInAs/GaAs pseudomorphic HEMTs with an InAs mole fraction as high as 35% in the channel has been successfully fabricated. The device exhibits a maximum extrinsic transconductance of 700 mS/mm. At 18 GHz, a minimum noise figure of 0.55 dB with 15.0 dB associated gain was measured. At 60 GHz, a minimum noise figure as low as 1.6 dB with 7.6 dB associated gain was also obtained. This is the best noise performance yet reported for GaAs-based HEMTs.<>     

A 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 12 /spl times/ 12 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode (APD) array. The mean breakdown voltage of the APD was 57.9 V and the standard deviation was less than 0.1 V. The mean dark current was /spl sim/2 and /spl sim/300 nA, and the standard deviation was /spl sim/0.19 and /spl sim/60 nA at unity gain (V/sub bias/ = 13.5 V) and at 90% of the breakdown voltage, respectively. External quantum efficiency was above 40% in the wavelength range from 1.0 to 1.6 /spl mu/m. It was /spl sim/57% and /spl sim/45% at 1.3 and 1.55 /spl mu/m, respectively. A bandwidth of 13 GHz was achieved at low gain.     

Al/sub 0.3/Ga/sub 0.7/As/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) doped-channel field-effect transistors (DCFET's)

The properties of both lattice-matched and strained doped-channel field-effect transistors (DCFET's) have been investigated in AlGaAs/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) heterostructures with various indium mole fractions. Through electrical characterization of grown layers in conjunction with the dc and microwave device characteristics, we observed that the introduction of a 150-/spl Aring/ thick strained In/sub 0.15/Ga/sub 0.85/As channel can enhance device performance, compared to the lattice-matched one. However, a degradation of device performance was observed for larger indium mole fractions, up to x=0.25, which is associated with strain relaxation in this highly strained channel. DCFET's also preserved a more reliable performance after biased-stress testings.<>     

Morphological and electrical characterization of SixCryCzBv thin films

Si_xCr_yC_zB_v thin films with several compositions have been studied for integration of high precision resistors in 0.8 μm BICMOS technology. These resistors, integrated in the back-end of line, have the advantage to provide high level of integration and attractive electrical behavior in temperature, for analog devices. The film morphology and the structure have been investigated through transmission electron microscopy analysis and have been then related to the electrical properties on the base of the percolation theory. According to this theory, and in agreement with experimental results, negative thermal coefficient of resistance (TCR) has been obtained for samples with low Cr content, corresponding to a crystalline volume fraction below the percolation threshold.Samples with higher Cr content exhibit, instead, a variation of the TCR as a function of film thickness: negative TCR values are obtained for thickness lower than 5 nm, corresponding to a crystalline volume fraction below the percolation threshold; positive TCR are obtained for larger thickness, indicating the establishment of a continuous conductive path between the Cr rich grains. This property seems to be determinant in order to assure the possibility to obtain thin film resistors almost independent on the temperature.     

Highly linear Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMTs

We report an Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMT with enhanced linearity. By engineering the channel region, i.e., inserting a 6-nm-thick AlGaN layer with 5% Al composition in the channel region, a composite-channel HEMT was demonstrated. Transconductance and cutoff frequencies of a 1 /spl times/100 /spl mu/m HEMT are kept near their peak values throughout the low- and high-current operating levels, a desirable feature for linear power amplifiers. The composite-channel HEMT exhibits a peak transconductance of 150 mS/mm, a peak current gain cutoff frequency (f/sub T/) of 12 GHz and a peak power gain cutoff frequency (f/sub max/) of 30 GHz. For devices grown on sapphire substrate, maximum power density of 3.38 W/mm, power-added efficiency of 45% are obtained at 2 GHz. The output third-order intercept point (OIP3) is 33.2 dBm from two-tone measurement at 2 GHz.     

Comparison between Pt/TiO2/Pt and Pt/TaOX/TaOY/Pt based bipolar resistive switching devices

Nonvolatile memories have emerged in recent years and have become a leading candidate towards replacing dynamic and static random-access memory devices. In this article, the performances of TiO₂ and TaO₂ nonvolatile memristive devices were compared and the factors that make TaO₂ memristive devices better than TiO₂ memristive devices were studied. TaO₂ memristive devices have shown better endurance performances (10⁸ times more switching cycles) and faster switching speed (5 times) than TiO₂ memristive devices. Electroforming of TaO₂ memristive devices requires~4.5 times less energy than TiO₂ memristive devices of a similar size. The retention period of TaO₂ memristive devices is expected to exceed 10 years with sufficient experimental evidence. In addition to comparing device performances, this article also explains the differences in physical device structure, switching mechanism, and resistance switching performances of TiO₂ and TaO₂ memristive devices. This article summarizes the reasons that give TaO₂ memristive devices the advantage over TiO₂ memristive devices, in terms of electroformation, switching speed, and endurance.     

Electrooptic ferroelectric Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films

We report on waveguiding and electrooptic properties of epitaxial Na/sub 0.5/K/sub 0.5/NbO/sub 3/ films grown by radio-frequency magnetron sputtering on Al/sub 2/O/sub 3/(11_02) single crystal substrates. High optical waveguiding performance has been demonstrated in infrared and visible light. The in-plane electrooptic effect has been recorded in transmission using a transverse geometry. At dc fields, the effective linear electrooptic coefficient was determined to 28 pm/V, which is promising for modulator applications.     

A 1 cm/spl times/1 cm In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode array

We report a 1 cm/spl times/1 cm array of 100 In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiodes (APD). The average breakdown voltage was 28.7 V with a standard deviation of less than 0.5 V. The distribution of breakdown voltage across the area followed a radial pattern consistent with a slight epitaxial growth nonuniformity. The mean dark current at a gain of 10, or 6.1 A/W, was 10.3 nA, and none of the 100 APDs had a dark current of more than 25 nA. The bandwidth at a gain of 10 was 6.2 GHz, and the maximum gain-bandwidth product was 140 GHz. This technology is ideally suited for next-generation three-dimensional imaging applications.