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.     

Si基光子器件的p-i-n电学结构模型及分析

为了设计研制基于载流子色散效应的Si基光子器件 ,本文针对Si基光子器件的电学结构,利用Silvaco的器件仿真工具Atlas,并根据 载流子色散理论, 结合有限差分(FD)法,建立了基于p-i-n结的电学结构模型。 同时,为了提高模型的实 际应用水平,采用0.18μm CMOS工艺线制作Si基马赫-曾德尔调制器(MZM), 并进行相应的实验验证与分析。本文工作将为从物理层面上优化Si基光子器件设计提供帮助 。     

日盲探测器高Al组分n-Al0.6Ga0.4N欧姆接触

研究了应用于日盲探测器的高Al组分Si掺杂n型Al0.6Ga0.4N与两层金属层Ti(20nm)/Al(100nm)之间的欧姆接触. 在制作金属电极前用煮沸王水对样片进行表面预处理,金属制作后再在N2氛围中做快速热退火处理. 使用高精度XRD测试样品表面特性,并对不同温度下的情况进行比较. 样品的比接触电阻率是用环形传输线模型通过I-V测试得到. 670℃下90s退火得到最优ρc为3.42E-4Ω·cm2. 将该处理方法应用到实际的背照式AlGaN p-i-n日盲探测器中,探测器的光谱响应度和反向特性等参数得到很大的优化.     

背照式GaN/AlGaN p-i-n紫外探测器的制备与性能

文章研究了p-GaN/i-GaN/n-A l0.3Ga0.7N异质结背照式p-i-n可见盲紫外探测器的制备与性能。器件的响应区域为310~365nm,最大响应率为0.046A/W,对应的内量子效率为19%,优值因子R0A达到1.77×108Ω.cm2,相应的在363nm处的探测率D*=2.6×1012cmHz1/2W-1。     

Drive current boosting of n-type tunnel FET with strained SiGe layer at source

Though silicon tunnel field effect transistor (TFET) has attracted attention for sub-60 mV/decade subthreshold swing and very small OFF current (I_OFF), its practical application is questionable due to low ON current (I_ON) and complicated fabrication process steps. In this paper, a new n-type classical-MOSFET-alike tunnel FET architecture is proposed, which offers sub-60 mV/decade subthreshold swing along with a significant improvement in I_ON. The enhancement in I_ON is achieved by introducing a thin strained SiGe layer on top of the silicon source. Through 2D simulations it is observed that the device is nearly free from short channel effect (SCE) and its immunity towards drain induced barrier lowering (DIBL) increases with increasing germanium mole fraction. It is also found that the body bias does not change the drive current but after body current gets affected. An I_ON of and a minimum average subthreshold swing of 13 mV/decade is achieved for 100 nm channel length device with 1.2 V supply voltage and 0.7 Ge mole fraction, while maintaining the I_OFF in fA range.     

具有新型电子传输层的有机薄膜电致发光器件

将8-hydroxy-quinolinato lithium(Liq)掺入4'7-diphyenyl-1,10-phenanthroline(BPhen)作为n型电子传输层(ETL),将tetrafluro-tetracyano-quinodimethane(F4-TCNQ)掺入4,4',4"-tris(3-methylphenylphenylamono)triphenylamine(m-MTDATA)作为p型空穴传输层(HTL),制作了p-i-n结构有机电致发光器件.为了检验传输层传导率的改善情况,制备了一系列单一空穴器件和单一电子器件.在引入BPhen:33wt% Liq作为ETL后,x% F4-TCNQ:m-MTDATA作为HTL后,器件的电流和功率效率明显改善.与控制器件(未掺杂)相比,性能最佳的掺杂器件的电流及功率效率分别提高了51%和89%,电压下降了29%.这是由于传输层传导能力的提高使得载流子在发光区域达到有效平衡.     

Very high-speed ultraviolet photodetectors fabricated on GaN

We report on the temporal and the frequency response of both metal-semiconductor-metal (MSM) and p-i-n ultraviolet photodetectors fabricated on single-crystal GaN. The best MSM devices show a fast 10–90% rise-time of ∼28 psec under comparatively low ultraviolet excitation of ∼0.1 W/cm² averagerirradiance. The fast-Fourier transform (FFT) of the pulse response data indicates a bandwidth, f_3dB, of ∼3.8 GHz at a reverse bias of 25 V. This agrees well with the direct frequency response measurement value of ∼3.5 GHz. For the p-i-n devices, we measured a rise-time of ∼43 psec at 15 V reverse bias for a 60 μm diameter mesa with 1 μm thick intrinsic region. The FFT of the p-i-n pulse response obtains f_3dB ≈1.4 GHz. Analysis in terms of reverse bias and geometric scaling indicates that the MSM photodetectors are transit-time limited. The p-i-n devices also show evidence of transit-time limited effects based on trends with respect to reverse bias and intrinsic region thickness. However, our larger area p-i-n devices show clear evidence of RC-limited behavior. Modeling of the temporal behavior indicates that a slow component in the time and frequency response data is a consequence of the hole drift velocity. We have also found preliminary evidence of microplasmic effects in the p-i-n devices.     

多晶PIN二极管及二极管串作良好工艺兼容并可移植ESD保护器件的研究

作为静电保护保护器件,多晶PIN二极管具有良好工艺兼容性及可移植的优点。文章制作并展示了多晶PIN二极管的反向击穿电压、漏电流及电容特性,同时通过正向及反向传输线脉冲电流电压特性评估了其静电保护能力。另外为了经一部降低电容并控制反向崩溃及正向开启电压对多晶PIN二极管串进行了研究。最后对器件特性进行了分析讨论,阐明了器件参数对性能的影响。     

High efficiency perovskite solar cells using a PCBM/ZnO double electron transport layer and a short air-aging step

Solution processed CH₃NH₃PbI_xCl_3–x based planar heterojunction perovskite solar cells with power conversion efficiency (PCE) above 14% are reported. The devices benefit from a phenyl-C₆₁-butyric acid methyl ester (PCBM)/ZnO double electron transport layer (ETL) as well as a short air-aging step. The role of the additional ZnO ETL is studied by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and secondary ions mass spectroscopy (SIMS). Apart from improving the energy level alignment, the ZnO layer blocks the reactions between the metal electrode and perovskite components, increasing the air stability of the device. A crucial step in our processing is a short air-aging step for the device, which significantly increases the device performance by reducing the recombination process. Since the ZnO nanoparticle layer requires no thermal annealing, the maximum temperature to fabricate the device can be kept below 100 °C, making this structure compatible with roll-to-roll processing on plastic films.     

Temperature and magnetic field effect on oscillations observed in GaInNAs/GaAs multiple quantum wells structures

The photoconductivity of p-i-n GaInNAs/GaAs multiple quantum well (MQW) mesa structures is investigated. When illuminated with photons at energy greater than the GaAs bandgap, a number of oscillations are observed in the current–voltage I–V characteristics. The amplitude and position of the oscillations is shown to depend upon the temperature, as well as upon the exciting wavelength and intensity. Due to the absence of the oscillations in the dark I–V and at temperatures above T = 200 K, we explain them in terms of photogenerated electrons escaping from quantum wells via tunnelling or thermionic emission.