III-V族化合物半导体整体多结级连太阳电池——光伏技术的新突破(续)

前面已提到,与Ge晶格匹配的GaInP2/Ga(In)As/Ge三结电池材料系统无论对于空间还是地面阳光,都不是最理想的选择。图8给出了三级子单纯的外量子效率光谱响应及AM0/AM1.5G阳光下光生电流密度按单位光子能量绘制的光谱分布曲线[32]。由于在Ga(In)As的吸收限(约880nm)以外,太阳光谱中仍有相当丰富的红外光可以被Ge底电池所利用,使其短路电流密度远远高于电流匹配的GaInP2/GaInAs两级顶电池。为了更有效地把太阳光能转变为电能,可以通过改变In/Ga组分比,调低GaInP2/GaInAs两级顶电池的带隙宽度。     

Ⅲ-Ⅴ族化合物半导体整体多结级连太阳电池——光伏技术的新突破(续)

3 基于GaAs的空间用多结级连太阳电池进一步的研究课题 3.1 用晶格失配的材料系统实现与太阳光谱更好的匹配 前面已提到,与Ge晶格匹配的GaInP2/Ga(In)As/Ge三结电池材料系统无论对于空间还是地面阳光,都不是最理想的选择.     

GaInP类异质结提升GaInP/GaInAs/Ge太阳电池效率的研究

基于不同有序度的GalnP材料制备出高/低带隙的发射区/基区结构被称之为同材料类异质结结构,其产生的特殊能带结构可以提高太阳电池效率.通过生长条件的优化,验证了GaInP材料的有序度变小,材料带隙从优化前1.868 eV提高到1.898 eV.采用该工艺条件制造了具有对应有序度的GalnP材料,分别作为GaInP/GaInAs/Ge三结太阳电池顶子电池的发射区/基区.测试结果表明,与参照电池比较,新结构太阳电池光照电流电压(LIV)特性参数在电流密度方面获得了明显的提高.     

32％效率三结砷化镓太阳电池设计与在轨应用

采用晶格小失配的GaInP/GaInAs/Ge三结砷化镓太阳电池结构,通过增加顶电池与中电池中In组分,选取带隙组合为1.87 eV/1.35 eV/0.67 eV的结构体系,使顶、中电池光吸收下限分别红移15和40 nm左右,提高了三结砷化镓太阳电池的电流密度,提升了太阳电池光电转换效率,研制出平均光电转换效率为32%(AM0,25℃)的三结砷化镓太阳电池。该太阳电池已成功应用于PakTES-1A卫星太阳电池阵,入轨初期由其SG1与SG5子阵在轨电流数据计算对比地面同工况测试结果,差异仅为-0.2%和0.5%。产品可用于后续航天器高效率太阳电池阵。     

离子源在太阳电池减反射膜沉积中的应用研究

在无烘烤条件下,使用离子源辅助沉积技术进行空间用三结砷化镓太阳电池(GaInP/GaInAs/Ge)的减反射膜沉积。对比不同离子源参数下的减反射膜薄膜折射率、太阳电池表面反射率、短路电流及转换效率增益,分析出当阳极电压为150～180 V、束流为5～6 A时可获得较好的增益效果。通过太阳电池外量子效率测试发现,由辅助沉积粒子所引起的电池结构损伤主要表现为顶结电池的光谱响应下降。     

键合集成AlGaInP/GaAs/InGaAsP/InGaAs太阳电池组分与厚度对效率的影响

寻找比传统晶格匹配GaInP/InGaAs/Ge结构具有很高效率的高效太阳电池体系是目前高效太阳电池研究重点。基于直接键合集成技术的AlzGa1-zInP/GaAs/In1-xGaxAsyP1-y/InGaAs四结太阳电池是一条有效的途径。该结构中In-GaAsP材料光学带隙可以在0.75～1.35 eV之间连续调节。作为一种新结构,一些关键点还是不清楚,比如考虑材料吸收系数与实际厚度限制下的带隙优化组合,子电池厚度与最高效率之间的耦合影响等,这些都对结构设计提出了新的挑战。采用半经验全局优化工具,研究了InGaAsP子电池组分和吸收系数比较小的InGaAs子电池厚度这两个因素对最高效率的影响,并对器件设计给出了一些方向性意见。     

InGaN/GaN多量子阱绿光发光二极管内量子效率研究进展

氮化镓基发光二极管(LED)具有绿色环保、节能降耗以及寿命长等优点,广泛应用在半导体照明、户外显示及可见光通信等领域。绿光LED有源区的In组分很高,会导致更高的缺陷密度和更大的极化电场,因此其内量子效率还不到蓝光LED的一半,是三基色照明急需解决的难点。本文对目前提升In Ga N/Ga N多量子阱绿光LED的关键技术和主要进展进行了综述。通过P型层生长工艺优化、变温量子阱及复合缓冲层等技术改善量子阱晶体质量,通过阶梯量子阱结构和半极性In Ga N量子阱生长技术来降低极化电场强度,最终提高绿光LED的内量子效率。     

含有布拉格反射器的GaInP/GaInAs/Ge太阳电池研究

通过数学方法,对中心波长为880 nm的布拉格反射器进行了理论计算和设计。采用MOCVD技术在Ge衬底上外延生长了15个周期,中心波长为880 nm的AlAs/GaAs结构的布拉格反射器,并且成功植入到GaInP/GaInAs/Ge结构的太阳电池中,使中间电池减薄到1.5μm,并且在AM0光谱下电池效率达到29.36%。     

超薄GaInP/GaInAs/Ge太阳电池研究

通过特殊的MOCVD技术和器件工艺,应用超薄衬底和对正常衬底的减薄两种方法,成功地制作出了80 mm厚的超薄GaInP/GaInAs/Ge结构的太阳电池。对太阳电池进行了相关的测试,并对实验结果进行了分析和讨论。     

基于台阶刻蚀工艺的GaInP/GaAs/Ge太阳电池激光划片研究

通过湿法台阶刻蚀工艺,在GaInP/GaAs/Ge太阳电池晶圆上按设计尺寸做成切割槽,继而采用皮秒或纳秒激光划切晶圆衬底,完成尺寸误差低于10μm的电池切割,该工艺制备的太阳电池性能与金刚石砂轮划片效果等同。和金刚石砂轮划片工艺相比,激光划片具有速度快、切割图形多样、维护周期短等优点。     

高效率非晶硅叠层太阳电池的研制

深入研究了a-Si/a-Si/a-SiGe三结叠层通讯卫星电池的制备技术.为了提高叠层电池的转换效率,提出改善n/i界面特性的缓冲层技术和高光敏性a-SiGe:H(F)薄膜的高氢气稀释比、低反应气压的淀积技术.通过工艺优化,研制出了AM1(100mW/cm~2)光照下转换效率为11.5%的a-Si/a-Si/a-SiGe三结叠层太阳电池.     

GaAs/Ge太阳电池组件无光照检测方法研究

分析了GaAs/Ge太阳电池在组合和测试方面存在的问题,阐述了GaAs/Ge太阳电池组件进行无光照检测的必要性。通过测试原理分析和试验确定了GaAs/Ge太阳电池组件无光照测试方案,并将测试结果和太阳模拟器(1 Sun,25℃)条件下测试结果进行对比分析,实践表明该方法具有简单、快捷、准确的特点。     

曲面硅太阳电池制备及性能分析

随着太阳电池的广泛应用,制备曲面硅太阳电池组件成为目前的一种应用趋势.但由于硅材料的机械性能使得其对于曲面电池组件制作存在困难,且效率较低.提出了一种任意曲面硅太阳电池组件制作方法,并通过太阳电池表面加装减反射软膜来提高其性能.实验测试曲面硅太阳电池的结果,显示其开路电压为1.945 V,短路电流为2.478 A,性能...     

Multiple-wavelength emission from In/sub x/Ga/sub 1-x/As-GaAs quantum wells grown on a nanoscale faceted GaAs substrate by molecular beam epitaxy

Multiple-wavelength photoluminescence (PL) spanning a 160-nm range from 980 to 1140 nm (77 K) has been obtained from In/sub x/Ga/sub 1-x/As-GaAs quantum wells (QWs) with varying In composition x on a nanoscale faceted (nanofaceted) GaAs substrate grown by molecular beam epitaxy. Five nanofaceted regions which consist of periodic [100]-(n11) (n = 3 or 1) facets along [011~] with different periods were prepared on a single substrate by interferometric lithography and selective growth of GaAs. The pattern period p was varied from infinity (large-area unpatterned) to 210 nm while the lateral width of the (n11) facet region was kept constant at /spl sim/180 to 200 nm within each period. A 5-nm-thick In/sub 0.23/Ga/sub 0.77/As layer was deposited on this multiple-period nanofaceted single GaAs surface in a single-run growth. Orientation-dependent migration and incorporation (ODMI) of In atoms [mass transport of incident In atoms from the (n11) to adjacent [100] facets] results in a variation of x of the In/sub x/Ga/sub 1-x/As layer section on the [100] facet as the width of the [100] facet was changed from /spl sim/20 to /spl sim/200 nm. ODMI induces a higher x on the [100] facet for smaller p. The PL exhibits a polarization dependence which is more pronounced for decreasing p [i.e., the width of [100] facet]. Consistent variations of the PL peak energy and linear polarization along the pattern direction confirm that ODMI results in a variation of the In composition and imply that the In/sub x/Ga/sub 1-x/As layer on a [100] facet has characteristics of a quantum wire as its width is decreased to /spl sim/20 nm for p = 210 nm. A possible application of nanopatterned growth to wavelength-division-multiplexing transmitters is discussed.     

A simulation study of short channel effects with a QET model based on Fermi–Dirac statistics and nonparabolicity for high-mobility MOSFETs

In this paper, the quantum confinement and short channel effects of Si, Ge, and \(\hbox {In}_{0.53}\hbox {Ga}_{0.47}\)As n-MOSFETs are evaluated. Both bulk and double-gate structures are simulated using a quantum energy transport model based on Fermi–Dirac statistics. Nonparabolic band effects are further considered. The QET model allows us to simulate carrier transport including quantum confinement and hot carrier effects. The charge control by the gate is reduced in the Ge and \(\hbox {In}_{0.53}\hbox {Ga}_{0.47}\)As bulk n-MOSFETs due to the low effective mass and high permittivity. This charge control reduction induces the degradation of short channel effects. In double-gate structures, different improvements of drain induced barrier lowering (DIBL) and subthreshold slope (SS) are seen. The double-gate structure is effective in the suppression of DIBL for all channel materials. The SS degradation depends on channel materials even in double-gate structure.     

聚光型高效率太阳能电池

本文阐述了聚光型太阳能发电系统高效率化和低成本化的可能性,以及由聚光型多结太阳能电池／模块技术开发所取得的成果。基于Ⅲ-Ⅴ族化合半导体技术的InG．aP／InGaAs／Ge3结聚光电池,最高的光电转换效率已达到40．7％,如利用4结、5结等多结化聚光电池．还可望实现50％的超高效率化。     

对Ga_(1-x)Al_xAs/GaAs太阳电池结构的一点新看法

用液相外延技术制备p-Ga_(1-x)Al_x/p-GaAs/n-GaAs结构的太阳电池,并获得AM1效率20.2%,AM0效率16%～17%.现已用研制出的GaAs电池单片,组装成组件,安装在我国1994年2月8日发射的实践4号卫星上作挂片实验.作者对此结构太阳电池提出一点新看法,同时提出北场GaAs太阳电池构想.     

Numerical modeling of loss mechanisms resulting from non‐uniform illumination in multijunction concentrator solar cells

Quasi‐3D distributed emitter models utilizing a unit cell‐based methodology have been successfully applied to the analysis of lateral current flow in solar cell emitter layers. However, the analysis of the specific loss mechanisms resulting from this flow has not been given adequate attention. In this work, a quasi‐3D model for the simulation of effects related to the lateral flow of current in a solar cell emitter layer, particularly under non‐uniform illumination, is developed. The model is applied to a specific case in which a GaInP/GaAs‐like two‐terminal solar cell is illuminated with a Lorentzian irradiance pattern, which is the expected pattern for parabolic trough concentrator. It is shown that bias‐point loss, which results from the variation in the local operating condition of the cell, is significant under highly non‐uniform illumination at low–moderate optical concentration. Understanding this loss mechanism is useful in considering trade‐offs related to the design of the optical concentrator system, as well as, the design of a grid electrode pattern for maximum power output. Copyright © 2013 John Wiley & Sons, Ltd.     

Lasing at 1.28 /spl mu/m of InAs-GaAs quantum dots with AlGaAs cladding layer grown by metal-organic chemical vapor deposition

We report the device characteristics of stacked InAs-GaAs quantum dot (QD) lasers cladded by an Al/sub 0.4/Ga/sub 0.6/As layer grown at low temperature by metal-organic chemical vapor deposition. In the growth of quantum dot lasers, an emission wavelength shifts toward a shorter value due to the effect of postgrowth annealing on quantum dots. This blueshift can be suppressed when the annealing temperature is below 570/spl deg/C. We achieved 1.28-/spl mu/m continuous-wave lasing at room temperature of five layers stacked InAs-GaAs quantum dots embedded in an In/sub 0.13/Ga/sub 0.87/As strain-reducing layer whose p-cladding layer was grown at 560/spl deg/C. From the experiments and calculations of the gain spectra of fabricated quantum dot lasers, the observed lasing originates from the first excited state of stacked InAs quantum dots. We also discuss the device characteristics of fabricated quantum dot lasers at various growth temperatures of the p-cladding layer.