利用Ni纳米岛模板制备半极性晶面GaN纳米柱

报道了在GaN表面以Ni纳米岛结构作为模板,利用电感耦合等离子(ICP)刻蚀制备GaN纳米柱的研究结果。原子力显微镜(AFM)测试结果表明,金属Ni薄膜在快速热退火(RTA)作用下形成了平均直径和高度大约分别为325 nm和70 nm的纳米岛状结构。通过电子扫描显微镜(SEM)照片看出,以GaN表面所形成的Ni纳米岛作为模板图形,通过控制ICP刻蚀时间,在一定的刻蚀时间内(2 min)获得有序的并拥有半极性晶面的GaN纳米柱阵列。这种新颖的半极性GaN纳米柱作为氮化物量子阱或者超晶格结构的生长模板,可以有效减小甚至消除极化效应,提高光电子器件的效率和性能。     

GaN衬底上纳米点阵列的制备及其应用研究

研究了纳米掩膜在材料外延生长及器件制备中的应用.通过电化学腐蚀和电子束蒸发方法在GaN表面生成Ni和SiO<,2>纳米点阵列,经过等离子体刻蚀在Ni/GaN模板上形成GaN纳米锥形结构;利用氢化物气相外延(HVPE)方法,在SiO<,2>/GaN模板上制备厚膜GaN材料.X射线衍射(XRD)和光致发光(PL)谱测试表明...     

Ni纳米粒子掩膜用于提高GaN基LED出光率的研究

以无水乙醇为溶剂、柠檬酸为分散剂,用超声分散技术配制Ni纳米粒子分散液;将分散液用旋涂的方法在GaN基发光二极管(LED)的ITO电流扩展层上制备单层Ni纳米粒子掩膜,采用ICP(inductively coupledplasma)干法刻蚀技术在ITO层上制作出表面粗化的结构。在20 mA工作电流下,与普通GaN基LED相比,这种ITO表面粗化的GaN基LED芯片发光强度提高了30%,并且对器件的电性能影响很小。结果表明,该表面粗化技术是一种工艺简单、成本低和能有效提高LED发光效率的方法。     

用表面粗化ITO的欧姆接触提高GaN基LED性能

应用ICP干法刻蚀工艺和自然光刻技术,制备了ITO表面粗化的GaN基LED芯片。聚苯乙烯纳米颗粒在干法刻蚀中作为刻蚀掩膜。通过扫描电镜(SEM)观察ITO薄膜的粗糙度,并且报道了优化的粗化工艺参数。结果表明,ITO表面粗化的GaN基LED芯片同传统的表面光滑的芯片相比在20 mA的驱动电流下,发光强度提高了70%。     

基于纳米压印技术的GaAs纳米柱阵列ICP刻蚀工艺及其光学特性研究

近年来,半导体纳米阵列结构材料因能激发光学共振及其优良的光电性能在光电子器件领域被广泛的应用。本文采用纳米压印技术制备具有一定直径和周期的SiO₂纳米柱作为掩膜层,采用ICP刻蚀制备了GaAs纳米柱阵列,重点研究了不同刻蚀条件处理工艺对纳米柱阵列形貌的影响,与表面无纳米结构的薄膜材料相比,其反射率得到明显的降低且最低约为3%,因此纳米阵列结构能有效的增强光吸收,具有极其优良的光电性能。     

基于胶体球掩模板法制备图形化蓝宝石衬底

制备并研究了纳米级图形化蓝宝石衬底.采用磁控溅射技术在蓝宝石衬底上沉积 SiO2薄膜,利用自组装方法在SiO2薄膜上制备单层聚苯乙烯(PS)胶体球阵列,利用感应耦合等离子体干法刻蚀将周期性PS胶体球的图形转移到SiO2薄膜上,通过湿法腐蚀制备了纳米级图形化蓝宝石衬底.利用扫描电子显微镜对胶体球掩膜、SiO2纳米柱掩膜和图形化蓝宝石衬底结构进行了观察,研究了湿法腐蚀蓝宝石衬底的中间产物对刻蚀的影响,分析了腐蚀温度和腐蚀时间对蓝宝石衬底的影响.结果表明,湿法腐蚀的中间产物会降低蓝宝石衬底的刻蚀速率.蓝宝石衬底的腐蚀速率随着腐蚀温度的升高而加快;在同一腐蚀温度下,随着腐蚀时间的增加,图形尺寸进一步减小.     

阳极氧化铝工艺用于提高LED的出光效率

使用纳米尺度的多孔阳极氧化铝(anodic aluminum oxide,AAO)作为刻蚀掩膜,刻蚀氧化铟锡(indium-tin oxide,ITO),形成纳米图形化表面,对于发光二极管的出光效率有明显的提升作用。AAO纳米掩膜的制备已广为报道,是纳电子学研究中常用的模板之一,工艺简单易行、可控性好。使用电感耦合反应离子刻蚀方法成功将纳米多孔结构转移到ITO上,形成ITO纳米结构。纳米图形化结构的引入使得器件有效减小了内部的全反射,在电压没有大幅提高,注入电流350 mA时,光学输出提高了7%。纳米尺度粗化结构LED与传统结构LED对比,提升了器件的外量子效率。     

HVPE生长的高质量GaN纳米柱的光学性能

GaN纳米材料因具有优异的晶体质量和突出的光学性能及发射性能,日益受到关注.研究了一种利用氢化物气相外廷(HVPE)系统生长高质量的GaN纳米柱的方法.使用镍作为催化剂,在蓝宝石衬底上生长出了GaN纳米柱.在不同生长时间和不同HC1体积流量下制备了多组样品,使用扫描电子显微镜(SEM)、X射线衍射(XRD)和光致发光(PL)谱对样品进行了分析表征.测试结果表明,在较低的HC1体积流量下,生长2 min的样品具有较高的晶体质量和较好的光学性质.讨论了不同生长阶段的GaN纳米结构发光特性的变化规律,认为纳米结构所产生的表面态密度大小差异会造成带边峰位的红移和展宽.     

金刚石纳米锥坑阵列结构的制备

采用电感耦合反应离子刻蚀(ICP-RIE)技术刻蚀金刚石薄膜,通过调整刻蚀功率、角度及时间等工艺参数,低成本且高效率地实现了排列整齐的圆形纳米锥坑阵列的可控化制备。对纳米锥坑的制备过程进行深入研究,发现可通过调节刻蚀角度与偏压功率控制氧等离子对金刚石进行高度方向性的刻蚀。荧光检测结果表明,直径为80～120 nm、深度为90～130 nm的纳米锥坑阵列结构可使金刚石薄膜内NV⁰色心的荧光强度增加21%,SiV^-色心的荧光强度增加49%。使用时域有限差分方法对增强原因进行探究,发现纳米锥坑对泵浦激发光有局限作用,并且可在纳米锥坑附近形成法布里-珀罗共振腔,使色心的自发辐射速率加快,进而增加其荧光强度。     

碳化硅ICP刻蚀的掩膜材料北大核心

SiC材料由于具有非常强的化学稳定性与机械硬度,不能用酸或碱性溶液对其进行腐蚀,在MEMS制备工艺中,通常采用干法刻蚀来制备SiC结构。针对干法刻蚀中遇到的问题,比较了光刻胶、Al和Ni等多种掩膜材料对SiC刻蚀的影响以及SiC与掩膜材料的选择比。实验证明,光刻胶作为掩膜,与SiC的选择比约为1.67,并且得到的台阶垂直度较差。Al与SiC的选择比约为7,但是致密性差,并且有微掩膜效应。金属Ni与SiC的选择比约为20,并且得到的台阶比较垂直且刻蚀形貌良好。最后,使用Ni作为掩膜材料对SiC压阻式加速度传感器的背腔和压敏电阻进行了电感耦合等离子体(ICP)刻蚀。     

Nano-Processing Techniques Applied in GaN-Based Light-Emitting Devices With Self-Assembly Ni Nano-Masks

We have developed a simple method to fabricate nanoscale masks by using self-assembly Ni clusters formed through a rapid thermal annealing (RTA) process. The density and dimensions of the Ni nano-masks could be precisely controlled. The nano-masks were successfully applied to GaN-based light-emitting diodes (LEDs) with nano-roughened surface, GaN nanorods, and GaN-based nanorod LEDs to enhance light output power or change structure properties. The GaN-based LED with nano-roughened surface by Ni nano-masks and excimer laser etching has increased 55% light output at 20 mA when compared to that without the nano-roughened process. The GaN nanorods fabricated by the Ni nano-masks and ICP-RIE dry etching showed 3.5 times over the as-grown sample in photoluminescence (PL) intensity. The GaN-based nanorod LEDs assisted by photo-enhanced chemical (PEC) wet oxidation process were also demonstrated. The electroluminescence (EL) intensity of the GaN-based nanorod LED with PEC was about 1.76 times that of the as-grown LED. The fabrication, structure properties, physical features, and the optical and electrical properties of the fabricated devices will be discussed.     

InGaN–GaN Nanorod Light Emitting Arrays Fabricated by Silica Nanomasks

We present a practical process to fabricate InGaN-GaN multiple quantum well nanorod structures. By using silica nanoparticles as the etch mask and followed by dry etching, nanorods with diameter 100 nm can be uniformly fabricated over the entire 2-in wafer. The photoluminescence spectra of the InGaN-GaN p-i-n nanorod structure are extracted at room and low temperatures. Also, discrete density of states can be observed at the temperature below 60 K. We further fabricate nanorod light emitting devices using a planarization approach to deposit p-type electrode on the tips of nanorods. Current-voltage curves and electroluminescent results of nanorod light emitting diode arrays are demonstrated.     

Optimization of the nanopore depth to improve the electroluminescence for GaN-based nanoporous green LEDs

GaN-based nanoporous green LEDs with different pore depth have been fabricated by using anodic aluminum oxide (AAO) as dry etching mask. The experimental results show that the electrical properties of the nanoporous LEDs with different pore depths are similar, but for the optical properties, the LEDs with nanopores extended to the p-GaN layer exhibits the best performance, if increase the depth to MQWs or decrease to the ITO layer will both decrease the light output power (LOP). By calculating the light extraction efficiency using three-dimensional (3D) finite-difference time-domain method, the decrease of the light output is mainly attributed to the reduced light extraction efficiency when the pore depth stop at ITO transparent layer instead of p-type layer, while if the depth reach the MQWs, the deterioration of the QWs which is caused by dry etching damage will play an important role. This optimization would give a valuable guidance to the surface structure design for nanostructured GaN-based LEDs, such as surface roughening, photonic crystal, or top-down fabricated surface-plasmon enhanced LEDs.     

低损伤ICP刻蚀技术提高GaN LED出光效率

首先分析了在制作GaN基LED时,采用干法刻蚀技术会对材料的表面和量子阱有源区造成损伤,影响了GaN基LED的内量子效率。针对这个问题,研究实验采用感应耦合等离子反应刻蚀(ICP-RIE)技术,分别选择了氯气/三氯化硼(Cl2/BCl3)气体体系和氯气/氩气(Cl2/Ar)气体体系,通过优化射频功率、ICP功率、气体流量以及相应的真空度,得到了良好的刻蚀端面,对于材料造成的损伤较低,得到更好的I-V特性。实验结果表明,采用低损伤的偏压功率刻蚀后制作的LED器件,出光功率提升一倍以上,同时采用Cl2/Ar气体体系,改善了器件的I-V特性,有效提高了LED的出光效率。     

硅衬底GaN基LED外延生长的研究

采用在AlN缓冲层后原位沉积SiN掩膜层,然后横向外延生长GaN薄膜.通过该法在硅衬底上获得了1.7 μm无裂纹的GaN薄膜,并在此基础上外延生长出了GaN基发光二极管(LED)外延片,其外延片的总厚度约为1.9 μm.采用高分辨率双晶X-射线衍射(DCXRD)、原子力显微镜(AFM)测试分析.结果表明,GaN薄膜(0002)面的半峰全宽(FWHM)降低到403 arcsec,其表面平整度得到了很大的改善;InGaN/GaN多量子阱的界面较平整,结晶质量良好.光致发光谱表明,GaN基LED峰值波长为469.2 nm.     

High-Speed GaN-Based Green Light-Emitting Diodes With Partially n-Doped Active Layers and Current-Confined Apertures

We demonstrate a high-speed GaN-based green light-emitting diode for plastic optical fiber (POF) communication applications. By using a combination of n-type doping and undoped In_xGa_1-xN/GaN based multiple quantum wells (MQWs), and a 76-mum-diameter current-confined aperture structure, we can obtain an extremely high electrical-to-optical (E-O) 3 dB bandwidth (~330 MHz), which is limited by the spontaneous recombination lifetime of the MQWs. A reasonable coupled power (-264 muW) can be simultaneously achieved for a 2 mm in diameter POF with a 0.5 numerical aperture (NA).     

基于空间控制的ICP量子阱混杂技术

本文提出了一种针对InP/InGaAsP材料,基于空间控制技术的ICP量子阱混杂方法。同一片晶片上带隙能量的偏移程度可以通过掩膜上图形的不同占空比灵活的控制。通过一组优化的参数包括ICP-RIE刻蚀深度,二氧化硅沉积厚度,退火过程等,一个样品上,同时实现了五个不同的蓝移,其中最大的蓝移量达到75nm。结果显示在单片集成器件特别是多带隙结构器件的制作中这是一种有效的方法。     

Characteristics and fabrication of nanohole array on InP semiconductor substrate using nanoporous alumina

Uniform arrays of nano-sized pore produced in porous alumina were transferred into InP substrates by inductively coupled plasma reactive ion etching (ICP-RIE). We observed a significant enhancement in the light output from InP substrate with nanohole arrays on the surface. Photoluminescence intensity of triangular arrays of air cylinders on InP substrate showed an enhancement up to 3 times compared with that from a raw InP substrate without such structure. The ICP-RIE technique using nanoporous alumina mask can be used as a prospective method in the fabrication of nanostructure materials for increasing the light output from semiconductor light emitting devices.     

Hot-electron induced degradations in GaN-based LEDs fabricated on nanoscale epitaxial lateral overgrown layers

We report investigations on the hot-electron hardness of GaN-based multiple quantum wells (MQWs) fabricated on nanoscale epitaxial lateral overgrown (NELO) GaN layers. This layer was deposited using a SiO₂ growth mask with nanometer-scale windows. The active regions of the devices consist of five-period GaN/InGaN MQWs. Structural analyses of the material indicate significant reduction in the threading dislocation density of the devices compared to the control which were fabricated without the use of the NELO GaN layers. The hot-electron degradation of the devices due to the application of a large dc. current was characterized by detailed examination of the electroluminescence (EL), I-V, thermoreflectance and the current noise power spectra of the devices as a function of the stress time. Significant improvements in the hot-electron hardness were observed in the device compared to the control.