基于氮化镓单晶的垂直p-i-n二极管性能研究

利用高质量自支撑GaN衬底,通过外延方法制备了垂直结构的GaN基p-i-n型二极管结构.通过对材料结构、杂质浓度分布以及对器件整流特性的研究,探究了影响垂直结构器件特性的关键因素.结果 表明,在同质外延的制备过程中,衬底表面的粗糙程度将使制备的环形结构具有不规则形状,这种不规则电极对垂直结构器件的性能将产生不利影响;此外,多种杂质在界面处聚集,进而形成平面漏电通道,是降低器件耐压值的主要因素.     

GaN基同型异质结IMPATT二极管噪声特性研究

针对p型GaN IMPATT制造工艺仍未成熟,提出了一种In0.4Ga0.6N/GaN n-n型异质结构来取代常规p-n结构,使GaN IMPATT二极管工作在IMPATT模式下。研究了这种n-n型In0.4Ga0.6N/GaN碰撞电离雪崩渡越时间(IMPATT)二极管的噪声特性,与同等条件下的传统GaN基p-n结IMPATT二极管作比较。结果表明,在不同偏置电流密度和不同InGaN层厚度下,该器件的噪声特性均好于传统p-n结构。结合器件交流输出特性可以得知,In0.4Ga0.6N/GaN同型异质结IMPATT器件不仅在功率效率上优于GaN p-n结构,其噪声性能表现亦优于传统GaN p-n结构,特别是在高频段的噪声特性优势更加明显。该研究可以为GaN基IMPATT器件的设计提供更多的思路和参考。     

Intermodulation Product and Switching Noise Amplitudes of a p-i-n Diode Switch in the UHF Band (Correspondence)

This correspondence describes some measurements of intermodulation product and switching noise amplitudes at UHF in a p-i-n diode switch.     

On the Origin of the Excess Low-Frequency Noise in Graded-Channel Silicon-on-Insulator nMOSFETs

The origin of the low-frequency noise in graded- channel silicon-on-insulator nMOSFET is studied as a function of the back-gate bias at a low drain-to-source bias. It is shown that an excess noise peak that is correlated with the peak in the transconductance can be observed. This excess noise is due to a generation-recombination component in the low-frequency range, which is suppressed when the back gate is in accumulation mode.     

PIN管控制电路功率容量的确定

PIN管控制电路的功率容量是一个重要的电路参数，必须全面考虑PIN管本身的功率容量和电路结构形式、施加的反向偏置电压、射频信号的频率和形式以及电路在系统中的匹配状况、工作环境和可靠性要求等各项因素综合确定。分析了对影响电路功率容量确定的各种因素，介绍了在射频系统中PIN管控制电路功率容量确定的综合方法。     

锗硅HBT BiCMOS工艺中的p-i-n开关二极管设计

介绍了一种集成在BiCMOS工艺的p-i-n开关二极管的器件。它由在STI下面的n型赝埋层作为p-i-n的n区,锗硅npn异质结双极型晶体管的重掺杂外基区作为p-i-n的p区。同时新开发了穿过场氧的深接触孔工艺用于赝埋层的直接引出,并采用p-i-n注入用于对i区进行轻掺杂。借助半导体工艺与器件仿真软件,得到了有源区尺寸、赝埋层到有源区的距离、p-i-n注入条件等关键工艺参数对p-i-n性能的影响。最后优化设计的p-i-n二极管,其在2.4 GHz频率下的指标参数,如插入损耗为-0.56 dB,隔离度为-22.26 dB,击穿电压大于15 V,它达到了WiFi电路中的开关器件的性能要求。     

基于电荷传输层优化的量子点发光二极管

采用溶液法旋涂薄膜、真空蒸镀铝电极,制备了ITO/PEDOT∶PSS/空穴传输材料/量子点/纳米氧化锌(ZnO Nanoparticles)/Al结构的量子点发光二极管(QLED)器件。对比了不同纳米氧化锌分散剂对器件性能的影响。当用乙醇和乙醇胺分散氧化锌时,对量子点层破坏较小,器件的亮度最高达22 940cd/m2,电流效率达28.9cd/A。研究了在聚乙烯咔唑(PVK)中掺杂不同比例4,4′-环己基二[N,N-二(4-甲基苯基)苯胺](TAPC)器件的发光特性。在PVK中掺杂TAPC材料能够促进器件空穴传输以及电子空穴注入平衡,当PVK∶TAPC=3∶1时,器件的空穴传输层形貌较为平整,亮度较高;当PVK∶TAPC=1∶1时,器件的开启电压最低。通过对器件膜层表面形貌以及电学、光学性能的对比,分析了电荷传输层优化对器件特性改善的原因。     

Comparison of GaN p-i-n and Schottky rectifier performance

The performance of GaN p-i-n and Schottky rectifiers fabricated on the same wafer was investigated as a function of device size and operating temperature. There was a significant difference in reverse breakdown voltage (490 V for p-i-n diodes; 347 V for the Schottky diodes) and forward turn-on voltage (~5 V for the p-i-n diodes; ~3.5 V for the Schottky diodes). Both types of device showed a negative temperature coefficient for reverse breakdown, with value -0.34±0.05 V·K^-1     

Current-voltage characteristics of GaN and AlGaN p-i-n diodes

The current-voltage characteristics of GaN and Al_0.08Ga_0.92N p-i-n diodes were investigated. The experimental p-i-n structures were grown by MOCVD on 6H-SiC with Si and Mg as dopants. The i region was formed by simultaneously doping with donor and acceptor impurities during growth. Analysis of the current-voltage characteristics showed that current flow in the p-i-n diodes is due to either drift of thermally excited holes or electron-hole recombination in the i region via impurity centers—just as predicted by the Ashley-Milnes theory. These impurity centers are attributed to Mg acceptor levels. Fiz. Tekh. Poluprovodn. 32, 369–372 (March 1998)     

An Improved Physics-Based Formulation of the Microwave p-i-n Diode Impedance

An improved formulation of the frequency-dependent impedance for p-i-n diodes from physical and geometrical parameters is presented. This work is addressed to diode designers and allows them to evaluate quickly and accurately the diode impedance. It comes in parallel with existing SPICE p-i-n diode model used in CAD software. Under forward bias conditions, important recombinations occur in the heavily doped end regions of thin p-i-n diodes that seriously affects the diode impedance. This effect is taken into account to increase the accuracy of existing numerical models and to extend their validity domain to any I-region thicknesses. This improvement has been validated by measurement results on a 5-mum I-region width silicon p-i-n diode     

Low-Frequency Noise Characteristics in Strained-Si nMOSFETs

The low-frequency (LF) (1/f) noise mechanism of strained-Si nMOSFETs grown on relaxed Si_1-xGe_x virtual substrates (VSs) has been investigated. It is found that the Si-cap thickness plays an important role in characterizing the 1/f noise mechanism. Ge out-diffusion effect and slight strain relaxation in Si-cap layer are responsible for the degradation of 1/f noise in strained-Si device with 10- and 20-nm-thick Si-cap, respectively. In addition, by choosing proper Si-cap thickness, experimental result shows that as Si-cap undergoes stronger tensile strain for higher Ge concentration VS, the correlated mobility fluctuation term in the modified carrier-number fluctuation model is more dominated for the 1/f noise     

Low-Frequency Noise Phenomena in Switched MOSFETs

In small-area MOSFETs widely used in analog and RF circuit design, low-frequency (LF) noise behavior is increasingly dominated by single-electron effects. In this paper, the authors review the limitations of current compact noise models which do not model such single-electron effects. The authors present measurement results that illustrate typical LF noise behavior in small-area MOSFETs, and a model based on Shockley-Read-Hall statistics to explain the behavior. Finally, the authors treat practical examples that illustrate the relevance of these effects to analog circuit design. To the analog circuit designer, awareness of these single-electron noise phenomena is crucial if optimal circuits are to be designed, especially since the effects can aid in low-noise circuit design if used properly, while they may be detrimental to performance if inadvertently applied     

High UV/solar rejection ratios in GaN/AlGaN/GaN p-i-n photodiodes

The solar-blind detection capability of heterostructure diodes employing an i-Al_0.33Ga_0.67N layer sandwiched between two doped GaN layers is investigated via simulations using MEDICI. It is shown that the introduction of quantum features, such as InGaN quantum wells and delta-doped regions of p-Al_0.33Ge_0.67N, can successfully suppress the current due to photogeneration in the low-bandgap GaN regions, leading to UV/solar rejection ratios of over three orders of magnitude     

GaN HFET中的噪声

从GaN异质结沟道阱中电子状态出发研究了HFET中的噪声产生机理.用沟道阱中子带间散射解释了迁移率起伏引起的1/f噪声.从电子状态转移及不同状态间的跃迁出发解释了各类噪声实验结果.建立了沟道阱能带与HFET噪声性能间的关联.运用正、负极化电荷剪裁了肖特基势垒、欧姆接触及内、外沟道的势垒和主阱及副阱阱宽和势垒高度,降低了栅流、欧姆接触和外沟道串联电阻,强化了沟道阱的量子限制,减弱了子带间散射.     

GaN基p-i-n器件振动噪声研究

振动环境中,GaN基p-i-n器件的噪声会急剧增加,这限制了器件的探测能力。利用力锤和振动台分别模拟冲击振动和随机振动环境,研究了器件噪声在不同振动条件下的变化规律。实验结果表明,在冲击振动中,器件噪声呈现出周期特性,但噪声幅度随着时间减小。器件噪声主要的频率成分为429Hz,此频率下的器件噪声与激励力的大小、振动加速度的幅度成线性关系。随机振动的实验结果也表明,振动环境中测量到的噪声随着随机振动功率谱密度的增大而线性增加。     

Low-Frequency Noise Characteristics in Ion-Implanted GaN-Based HEMTs

Low-frequency noise characteristics in ion-implanted GaN/AlGaN/GaN and AlGaN/GaN HEMTs were investigated. The normalized spectral noise density was about 6 dB lower in GaN/AlGaN/GaN HEMTs than in AlGaN/GaN HEMTs. The normalized spectral noise density dependence on the gate length Lg indicates that the main origin of low-frequency noise is at the region under the gate in both devices. The Hooge parameters alphaH for both devices are on the order of 10^-1-10^{- 2}. The ion implantation process introduces a lot of defects in the source/drain regions, but the values of alphaH are comparable with those for conventional GaN-based HEMT devices. The values of alphaH are also lower in GaN/AlGaN/GaN HEMTs than in AlGaN/GaN HEMTs, which is due to the decrease of surface potential fluctuations in GaN/AlGaN/GaN HEMTs.     

Noise in IMPATT Diode Amplifiers and Oscillators

The results of experimental and theoretical investigations of the noise characteristics of lMPATT diode amplifiers and oscillators are presented. The oscillator noise is shown to consist of three different contributions: modulation noise, selectively amplified primary noise, and conversion noise. The influence of the active device nonlinearity and load circuit parameters is discussed in detail. The experimental results are in good agreement with the theoretical predictions. It is especially pointed out that the large correlation between AM and FM fluctuations, usually measured in IMPATT oscillators, indicates nonoptimum AM noise performance. Experimental techniques for achieving optimum AM noise performance are demonstrated (orthogonal noise tuning). By a simple extension of the model, the noise behavior of an injection phase-locked oscillator can be described. The calculated AM and FM noise power spectra for the synchronized oscillator are also shown to be in good agreement with experimental results. Finally the signal-to-noise ratio for current modulated IMPATT oscillators is investigated and optimization is demonstrated.     

Electrical properties and spectra of deep centers in GaN p-i-n rectifier structures

GaN p-i-n rectifiers with 4 μm thick i-layers show typical reverse breakdown voltages of 100–600 V. We have studied the temperature dependence of current-voltage characteristics in these diodes, along with hole diffusion lengths and the deep level defects present. Generally we find that i-layer background doping varies significantly (from <10¹⁴ cm⁻³ to 2–3×10¹⁶), which influences the current conduction mechanisms. The hole diffusion lengths were in the range 0.6–0.8 μm, while deep level concentrations were ∼10¹⁶ cm⁻³.