Photoresponse of the In0.3Ga0.7N metal-insulator-semiconductor photodetectors

In0.3Ga0.7N metal-insulator-semiconductor （MIS） and metal-semiconductor （MS） surface barrier photodetectors have been fabricated. The In0.3Ga0.7N epilayers were grown on sapphire by metalorganic chemical vapour deposition （MOCVD）. The photoresponse and reverse current-voltage characteristics of the In0.3Ga0.7N MIS and MS photodetectors were measured. A best zero bias responsivity of 0.18 A/W at 450 nm is obtained for the In0.3Ga0.7N MIS photodetector with 10 nm Si3N4 insulator layer, which is more than ten times higher than the In0.3Ga0.7N MS photodetector. The reason is attributed to the decrease of the interface states and increase of surface barrier height by the inserted insulator. The influence of the thickness of the Si3N4 insulator layer on the photoresponsivity of the MIS photodetector is also discussed.     

GaN1-xPx三元合金的红外谱

对GaN1-xPx三元合金进行了红外谱的测试和拟合. 分析结果表明在GaN1-xPx三元合金中存在两个彼此竞争的机制制约着载流子浓度的变化. 一个是来自等电子陷阱的影响，它将减少三元合金中载流子的浓度；另一个来自缺陷的影响，它将增加三元合金中载流子的浓度. 对合金介电函数的倒数的虚部进行了计算，其结果显示，随着合金中P组分比的增加，纵向光学声子-等离激元（LPP）耦合模式向高频方向移动，同时LPP模式线宽逐渐增宽，说明随着合金中P组分比的增加，LPP模式的耦合作用增加，阻尼增强.     

Surface States in the AlxGa1-xN Barrier in AlxGa1-xN／GaN Heterostructures

Frequency-dependent capacitance-voltage (C-V) measurements have been performed on modulation-doped Al0.22 Ga0.78N/GaN heterostructures to investigate the characteristics of the surface states in the AlxGa1-xN barrier. Numerical fittings based on the experimental data indicate that there are surface states with high density locating on the AlxGa1-xN barrier. The density of the surface states is about 10^12cm^-2eV^-1, and the time constant is about 1μs. It is found that an insulating layer (Si3N4) between the metal contact and the surface of AlxGa1-xN can passlvate the surface states effectively.     

GaN1-x Px三元合金的红外谱

对GaN1-xPx三元合金进行了红外谱的测试和拟合.分析结果表明在GaN1-xPx三元合金中存在两个彼此竞争的机制制约着载流子浓度的变化.一个是来自等电子陷阱的影响,它将减少三元合金中载流子的浓度;另一个来自缺陷的影响,它将增加三元合金中载流子的浓度.对合金介电函数的倒数的虚部进行了计算,其结果显示,随着合金中P组分比的增加,纵向光学声子-等离激元(LPP)耦合模式向高频方向移动,同时LPP模式线宽逐渐增宽,说明随着合金中P组分比的增加,LPP模式的耦合作用增加,阻尼增强.     

Solar-blind ultraviolet band-pass filter based on metal–dielectric multilayer structures

Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of ＂transparent metal＂. The filter consisting of Al/SiO2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period.     

基于单片机的可见光及紫外光强探测系统

BH750FVI是一种具有I2C总线接口的环境光强探测芯片,UVM-30是一种具有线性电压输出的紫外线探测模块.几乎不需要其他外围电路,采用这两种器件就可以与单片机构成一种涵盖从紫外到可见光的光强探测系统.本文详细介绍了这两种探测器的性能特点及其与单片机STC12C5608AD的连接方式;给出了单片机对这两种探测器的控制、光强数据的获取、以及数据显示等方法.采用具有数字接口或规格化输出的探测器构成的测量系统,结构紧凑,可靠性和稳定性都很高.     

GaN基肖特基二极管的场板工程

The practical design of GaN-based Schottky barrier diodes（SBDs） incorporating a field plate（FP） structure necessitates an understanding of their working mechanism and optimization criteria.In this work,the influences of the parameters of FPs upon breakdown of the diode are investigated in detail and the design rules of FP structures for GaN-based SBDs are presented for a wide scale of material and device parameters.By comparing three representative dielectric materials（SiO₂,Si₃N₄ and Al₂O₃） selected for fabricating FPs,it is found that the product of dielectric permittivity and critical field strength of a dielectric material could be used as an index to predict its potential performance for FP applications.     

背势垒对InAlN/GaN异质结构中二维电子气的影响

利用有效质量理论自洽求解Poisson和Schrdinger方程理论研究了背势垒插入层对InAlN/GaN晶格匹配异质结构的电学性能的影响。研究表明,对于In0.17Al0.83N/AlN/GaN的异质结构,AlN的临界厚度为2.43 nm。此时,异质结中二维电子气(2DEG)浓度达到2.49×1013 cm-2,且不随势垒层厚度的变化而变化。重点模拟研究了具有背势垒的InAlN/AlN/GaN/AlGaN/GaN和InAlN/AlN/GaN/InGaN/GaN两种结构的能带结构和2DEG的分布情况。理论结果表明,采用AlGaN背势垒结构时,对于AlGaN的任意Al组分,GaN沟道层导带底能量均被抬升,增强了AlN/GaN三角势阱对2DEG的限制作用,提高了电子迁移率。采用InGaN/GaN作为背势垒结构,当InGaN厚度为2或3 nm时,三角势阱中的2DEG随InGaN中In组分的增加先升高后降低,这主要是由于GaN/InGaN界面处产生的正极化电荷的影响,引起电子在AlN/GaN三角势阱和InGaN/GaN势阱之间的分布变化。     

InN薄膜的退火特性

对InN薄膜在氨气氛下的高温退火行为进行了研究.利用XRD,SEM和XPS对样品进行了分析.结果表明,InN薄膜的结晶质量和表面形貌并不随退火温度单调变化.由于高温退火时N原子的挥发,剩下的In原子在样品表面聚集形成In颗粒.当退火温度高于425℃时,In原子的脱吸附作用增加,从而导致样品表面的In颗粒在退火温度高于425℃时逐渐减少.XRD和SEM结果表明In颗粒密度最高的样品具有最差的结晶质量.这种现象可能是由于In颗粒隔离了其下面的InN与退火气氛的接触,同时,金属In和InN结构上的差异也可能在InN中导致了高密度的结构缺陷,从而降低了InN薄膜的结晶质量.     

InxGa1-xN合金薄膜In的表面分凝现象

用MOCVD方法在α-Al2O3(0001)衬底上外延生长了InxGa1-xN合金薄膜.测量结果显示:所制备的InxGa1-xN样品中In的组分随外延生长温度而改变,生长温度由620℃升高到740℃,In的组分由0.72降低到0.27.这是由于衬底温度越高,In进入InxGa1-xN薄膜而成键的效率越低.样品的X射线衍射谱和X射线光电子能谱均显示:在生长温度为620℃和690℃时所生长的InxGa1-xN样品中均存在明显的In的表面分凝现象;而生长温度升至740℃时所得到的InxGa1-xN样品中,In的表面分凝现象得到了有效抑制.保持生长温度不变而将反应气体的Ⅴ/Ⅲ比从14000增加到38000,In的表面分凝现象也明显减弱.由此可以认为,较高的生长温度使得In原子的表面迁移能力增强,In原子从InxGa1-xN表面解吸附的几率增大,而较高的Ⅴ/Ⅲ比则能增加N与In成键几率,从而有利于抑制In的表面分凝.