Polarity Control and Transition of GaN in MOCVD

Polarity of GaN epilayer grown on nitridated sapphire substrate and the possibility of polarity manipulation are investigated.GaN films grown on nitridated sapphire substrate show N polarity,and the N polarity films can be successfully converted to Ga polar by adding a TMAl flow before growth of low temperature buffer layer.Coaxial impact collision ion scattering spectroscopy (CICISS) is used to character the polarity. A "two atom layers of Al" model is tentatively proposed to explain the polarity convers...福建省自然科学基金重点资助项目 (E982 0 0 0 1

Device Quality GaN on Sapphire Grown by Three-step MOCVD

在传统的二步MOCVD外延生长的基础上 ,报道了一种在低压MOCVD中用三步外延生长GaN材料的新方法 ,它在生长低温缓冲层前 ,用原子层的方法生长一层高质量的AlN层来减少Al2 O3与GaN缓冲层之间的应力以提高缓冲层的质量 ,从而提高外延层GaN的质量 ,达到器件制作的要求福建省自然科学基金重点资助项目 (E982 0 0 0 1

GaN Polarity and Its Measurement and Application

【中文摘要】 GaN在 (0 0 0 1)方向是一种极性极强的半导体材料 ,它具有极强的表面特征 ,是目前发现的最好的压电材料 ,而GaN的极性呈现出体材料的特征 ,它的测量要用一些特殊的方法 ,它的不同特征也给我们提供了广泛的应用前景。总结了到目前为止国外这一方面的研究结果 【英文摘要】 GaN is a kind of material with very strong polarity. It offers different characteristics for different polarity GaN.For example, it is the best piezoelectric material ever discovered.The polarity of GaN exhibits the characteristic of bulk materials.Some special measuring methods are used to characterize the polarity.The polarity characteristics,and its measurement and application of GaN are reviewed in this paper

Enhancement of Photon Extraction Efficiency of GaN-based LED by Lateral Surface Roughening

通过对传统结构lEd出光分析,提出采用侧面粗化来提高gAn基lEd出光效率的方法,使用蒙特卡罗光子追踪方法对器件出光效率进行了模拟。结果表明:粗化侧面为三角状、底角为55°时出光效率最高,随机粗化可以获得比固定角度粗化更高的出光效率,同时降低材料的吸收系数可以提高lEd的出光效率,在吸收系数为10/CM时,经过粗化后的lEd出光效率可以达到46.1%。模拟结果证明侧面粗化可以较大地提高lEd的出光效率。By analyzing the light output of conventional LED,a method of lateral surface roughening was proposed to improve the extraction efficiency of GaN-based LED and Monte Carlo photon tracking method was used to simulate the extraction efficiency.The simulation results show that when the lateral surface is triangular-shaped,the extraction efficiency of 55° rough angle reaches the highest,and random roughening can get higher efficiency than stable roughening angle.Also,reducing the absorption coefficient of the material can enhance the extraction efficiency of LED highly,and when the absorption coefficient is 10/cm,the extraction efficiency of lateral surface roughening LED can get 46.1%.国家自然科学基金项目(60276029);国家“863”计划项目(2004AA311020;2006AA032409);福建省科技项目和基金资助项目(2006H0092;A0210006;2005HZ1018

Research and progress of ohmic contact to p-type GaN

【中文文摘】宽带隙的GaN作为半导体领域研究的热点之一,近年来发展得很快。p型GaN的欧姆接触问题一直阻碍高温大功率GaN基器件的研制。本文讨论了金属化方案的选择、表面预处理和合金化处理等几个问题,回顾了近年来p型GaN欧姆接触的研究进展。 【英文文摘】The wide-bandgap GaN has been extensively investigated and developed rapidly in recent years. But difficulty in obtaining low-resistance ohmic contacts to p-type GaN blocks the development of high temperature, high power GaN-based devices. Choice of metallization scheme, surface pretreatment and alloying process are discussed. The progress of ohmic contacts to p-type GaN are reviewed.国家自然科学基金项目(60276029); 福建省自然科学基金项目(A0210006

The calculation of gain matrix element of InGaAs/InP strain quantum well by using K·P method

应用k·P微扰法计算能带的基本方法，在考虑偏振随波矢变化的情况下，分别计算了无应变、1%压缩应变和1%伸张应变下4.0nM阱宽IngAAS/InP量子阱的增益矩阵元。计算表明，增益矩阵元的偏振因子随波失的变化而发生很大的变化。Taking TM and TE polarization into account,calculations of gain matrix elements are respectively made For unstrain,1% tensile strain and 1% compressive strain InGaAs/InP quantum well with the well width of 4.0 nm by means of K·P method For calculating energy band.The result shows that the gain matrix elements change dramatically with the variation of wave vector

Temperature Distribution Analytical Calculation for the Laser Lift-off of GaN/Al_2O_3 Material

【中文文摘】分析了脉冲激光作用下GaN的衬底剥离过程。利用简化的一维模型,给出一种比较直观的脉冲激光辐照下GaN/Al2O3材料温度分布的解析形式,得到了分界面温度和脉冲宽度的关系。表明,单脉冲作用下分界面的温度与加热时间的平方根成正比,并得出脉冲过后随着深度变化温度梯度的分布。在连续脉冲作用时,分界面的温度呈锯齿状不断升高。 【英文文摘】The process of laser lift-off of GaN thin films from substrates was analysed.A temperature distribution analytical calculation form of the GaN/Al_2O_3 material irradiated by pulsed laser was presented under one dimension,and the temperature calculation form of different interface was obtained.The results show that the temperature of interface is in proportion to the square root of time when the material is irradiated by single pulse laser,however,it increases saw-like when the material is irradiated by continuous pulse laser.国家自然科学基金资助项目(60276029); 福建省自然科学基金资助项目(A0210006)资助项

The Study on Multiple Quantum Well of TensileStrained InGaAs/InP Grown by LP-MOCVD

首先从理论上研究了在应变情况下量子阱中能级的计算，然后利用lP-MOCVd研究了IngAAS/InP组份的控制及生长条件，最后生长伸张应变为0.5%的四个量子阱IngAAS/InP结构材料，利用Pl光谱测量得最小阶宽为1.8nM。The energy levels of quantum well (QW) under diFFerential strain have been calculated,the composition and growth rate of InGaAs matched with InP have been studied by Low Pressure Metallorganic Chemical Vapour Deposition (LP-MOCVD).Four-QW InGaAs/InP with 0.5% tensile strain has been grown.The narrowest well width is 1.8 nm by PL spectroscopy measurement

Study of Optical Characteristics of InGaN/GaN MQW LED Depended on Growth Temperature

利用低压MOCVD系统,在蓝宝石衬底上外延生长了InGaN/GaN多量子阱蓝紫光LED结构材料。研究了生长温度对有源层InGaN/GaN多量子阱的合金组分、结晶品质及其发光特性的影响。结果表明当生长温度从730℃升到800℃时,LED的光致发光波长从490 nm移到380 nm,室温下PL谱发光峰的半高全宽从133 meV降到73 meV,表明了量子阱结晶性的提高。高温生长时,PL谱中还观察到了GaN的蓝带发光峰,说明量子阱对载流子的限制作用有所减弱。研究表明,通过改变生长温度可以对LED发光波长及有源层InGaN的晶体质量实现良好的控制。A series of blue-violet LEDs with InGaN/GaN multi-quantum-wells(MQWs) structure were grown by low-pressure metalorganic chemical vapor deposition(LP-MOCVD).The growth temperature of the active layer is very important for the indium concentration,crystal quality and optical properties of the sample.The emission wavelength over the range of 490~380 nm were achieved by varying the growth temperature between 730 ℃ and 800 ℃.And the full width at half of maximum of the photoluminescence and electricaluminescence spectrum were studied as a function(FWHM) of the growth temperature.Analysis of the relation between the emission spectrum and the growth temperature indicated that the high crystal quality and the expected emission wavelength can be achieved by controling the growth temperature of the active layer.国家自然科学基金项目(60276029);; 国家“863”计划项目(2004AA311020,2006AA032409);; 福建省科技项目(2006H0092,A0210006,2005HZ1018

Reduce Ohmic Contact Resistance to p-GaN Using InGaN/AlGaN Superlattice

提出用P-IngAn/AlgAn超晶格作为P-gAn的接触层来获得低阻欧姆接触。通过一维薛定谔方程和泊松方程的自洽求解,得到了在极化效应影响下的IngAn/AlgAn,IngAn/gAn和gAn/AlgAn三种超晶格中Mg杂质离化率的空间分布。计算发现IngAn/AlgAn超晶格具有最高的Mg杂质离化率及最佳的空穴局域作用。最后,利用P-IngAn/AlgAn超晶格实验上实现了比接触电阻率为7.27x10-5Ω.CM2的良好欧姆接触。In order to achieve a smaller Ohmic contact resistance,p-InGaN/AlGaN superlattice was proposed to be used as the cap-layer of p-GaN.By making use the self consistent Poisson-Schrodinger calculations,obtained were the distributions of the ionization rate of Mg dopant in InGaN/AlGaN,InGaN/GaN and GaN/AlGaN superlattices when taking into account of the effect of polarization.It was found that the InGaN/AlGaN superlattice cap-layer had the largest ionization rate of Mg and the best confinement of the holes.Finally,the specific contact resistance of 7.27×10-5 Ω·cm2 was realized.国家自然科学基金项目(60276029);国家“863”计划项目(2004AA311020;2006AA032409);福建省科技项目(2006H0092;A0210006;2005HZ1018