渡越时间方法测量聚合物材料的载流子迁移率

介绍了渡越时间方法的测量原理,讨论了激发光源的波长、单脉冲能量、脉冲宽度以及测量电路的积分时间常数、聚合物材料的光生载流子率、样品的制备、探测器的选取等测试条件对聚合物材料载流子迁移率测量结果的影响。实验表明,利用渡越时间方法测量聚合物材料载流子迁移率,只有严格选取合适的测量条件,才可获得准确、可靠的测试结果。     

载流子迁移率测量的光电方法

本文评述了载流子迁移率测量的各种方法,着重介绍了光电测量的渡越时间(TOF)方法,并对几种新的含偶氮基、硝基及咔唑基的光电功能材料进行了测量,给出了迁移率的测量结果.     

载流子迁移测量的光电方法

本文评述了载流子迁移率测量的各种方法,着重介绍了光电测量的渡越时间（TOF）方法,并对几种新的含偶氮基,硝基及咔唑基的光电功能材料进行了测量,给出了迁移率的测量结果。     

8-羟基喹啉铝本征薄膜的制备与性质研究

8-羟基喹啉铝属于有机半导体材料,在太阳能电池应用领域有较为广阔的应用前景。为了研究8-羟基喹啉铝载流子输运动力学信息,在恒温条件下制备了8-羟基喹啉铝薄膜,采用X射线衍射分析方法对薄膜的性质进行了分析,采用渡越时间方法对影响其载流子迁移率的实验条件进行了理论分析和实验验证。结果表明,在308K~338K温度范围内,8-羟基喹啉铝的载流子输运规律符合浅陷阱模型;取样电阻小于15kΩ及光脉冲能量低于3.5μJ时,载流子渡越时间保持恒定,测试结果可靠。这一结果对有机太阳能电池的制备是有帮助的。     

共轭聚合物中载流子迁移率的变温飞行时间检测

载流子迁移率是标定共轭聚合物光电器件性能的重要参数,在数值上其大小远小于传统半导体材料,所以常常用飞行时间方法来测量。利用自行搭建的变温飞行时间检测系统,能够准确地测量聚合物中载流子的迁移率。从原理和实践上,讨论了影响检测结果的限制因素和关键参数,其中包括光生载流子数量、薄膜样品厚度、激发光脉冲宽度、检测外电路的响应时间、载流子在电介质中的弛豫时间和对放大器探测器频率的限制等。只有选取恰当的实验参数才能够获得准确可靠的检测结果。     

n型HgCdTe载流子双极迁移率测量

介绍了两种测量半导体材料载流子双极迁移率的原理和方法。用载流子漂移实验方法测量了ｎ型Ｈｇ１－ｘＣｄｘＴｅ（ｘ＝０．２）材料在８０Ｋ时的双极迁移率，讨论了测量条件对双极迁移率的影响。     

InSb光电导太赫兹源材料性质及辐射场研究

为了研究锑化铟(InSb)半导体材料光电导太赫兹辐射过程,用数值计算方法分析材料内载流子迁移率和表面电流,以及不同性质抽运激光器对太赫兹波近场强度的影响,用宏观电磁场理论和微观半导体理论分析材料表面电流,比较了InSb和GaAs材料的太赫兹波功率谱曲线。结果表明,InSb材料载流子弛豫时间越长,载流子迁移率越大;表面电流与载流子寿命和弛豫时间成正比;宏观电磁场理论更适于分析表面电流;抽运激光饱和能量密度越大,太赫兹近场辐射强度越强;抽运激光脉冲宽度越短,太赫兹近场辐射强度越强;InSb光电导辐射太赫兹波功率比GaAs高。该结果为基于InSb光电导太赫兹辐射源的研究奠定了一定的基础。     

SiGe HBT基区渡越时间研究

对基于SiGe HBT基区本征载流子浓度和电子迁移率依赖于掺杂、基区Ge组分分布和速度饱和效应的基区渡越时间进行了研究。结果表明,相同Ge组分条件下,基区渡越时间bτ随WB由100 nm减薄到50 nm,降低了74.9%;相同WB,Ge组分为0.15比0.1 Ge组分的bτ减小了33.7%。该研究与其他文献的结果相吻合,可为SiGe HBT基区设计提供一定的理论指导。     

GD非晶硅电子迁移率的测量

本文介绍用“渡越时间”法测量辉光放电硅烷生长的本征非晶硅材料的电子迁移率。讨论了电场强度和注入光强度对瞬态光电流的影响。由于制备条件的不同,a-Si:H材料中电子迁移率在0.3～1.2cm~2/V.s之间。由于非晶硅材料中局域态对电子的陷阱作用,电子陷阱的释放弛豫时间均大于1μs。     

小功率晶体管参数测量原理与方法(二)

三、频率特性参数测量表征晶体管频率的参数有f_α、f_β、f_r和f_max,在这里着重介绍特征频率f_r的意义、测量原理和方法.1.晶体管特征频率f_r及其测量方法在晶体管中,当载流子从发射极注入到集电极输出需要一定时间,这个时间通常称为“渡越时间”.渡越时间愈短,表明晶体管工作的频率愈高.渡越时间与特征频率f_r之间的关系为:     

Transient space-charge-perturbed currents in organic materials: A Monte Carlo study

The transient current holds rich information about carrier transport and is used to derive charge mobility in the time-of-flight (TOF) measurement. Because carriers have finite charge, all transient currents are space-charge-perturbed (SCP). Previous theories of transient SCP currents are derived by neglecting diffusion and assuming a constant mobility, which is unfit for organic materials because of the hopping behavior of carriers. Due to the lack of knowledge, we do not fully understand the results from TOF experiments, which hinders the understanding of the charge transport mechanisms. Here, we perform Monte Carlo simulations of multi-particle carrier movement to study the transient SCP currents in organic materials. Coulomb interactions are calculated, and it is assumed that multiple carriers cannot occupy the same site simultaneously. Our results show that space-charge perturbation has two opposite effects on charge transport. In most cases, the net result is slower carrier movement, which suggests that TOF measurements under SCP conditions underestimate the charge mobility of organic materials.     

Charge‐Carrier Density Independent Mobility in Amorphous Fluorene‐Triarylamine Copolymers

A charge‐carrier density dependent mobility has been predicted for amorphous, glassy energetically disordered semiconducting polymers, which would have considerable impact on their performance in devices. However, previous observations of a density dependent mobility are complicated by the polycrystalline materials studied. Here charge transport in field‐effect transistors and diodes of two amorphous, glassy fluorene‐triarylamine copolymers is investigated, and the results explored in terms of a charge‐carrier density dependent mobility model. The nondispersive nature of the time‐of‐flight (TOF) transients and analysis of dark injection transient results and transistor transfer characteristics indicate a charge‐carrier density independent mobility in both the low‐density diode and the high‐density transistor regimes. The mobility values for optimized transistors are in good agreement with the TOF values at the same field, and both have the same temperature dependency. The measured transistor mobility falls two to three orders of magnitude below that predicted from the charge‐carrier density dependent model, and does not follow the expected power‐law relationship. The experimental results for these two amorphous polymers are therefore consistent with a charge‐carrier density independent mobility, and this is discussed in terms of polaron‐dominated hopping and interchain correlated disorder.     

Time of flight transient analysis in a molecular doped polymer using a dispersive-trapping formalism

The spatio-temporal spreading features of charge packets from time of flight (TOF) current transients in a molecular doped polymer system are analysed based on TOF current modelling and experimental results related to the thermal and electric field dependences of the dispersion parameters as well as the charge carrier mobility. The parameters describing the charge spatial spread are the velocity distributions within the moving charge packet, the trapping time and the trapping lengths. These parameters supplement our understanding of charge transport in these systems in addition to our previous experimental mobility investigations.     

多晶硅导电材料的1/f噪声模型研究

在多晶硅导电材料的1/f噪声迁移率涨落、载流子数涨落机制和模型的基础上,修正了基于迁移率涨落机制的噪声模型。通过分析材料中载流子输运的实际物理过程,论证了产生1/f噪声的两种机制同时存在于多晶硅材料中,提出建立多晶硅导电材料1/f噪声双机制不同掺杂浓度统一模型的思路。     

Contactless charge carrier mobility measurement in organic field-effect transistors

With the increasing performance of organic semiconductors, contact resistances become an almost fundamental problem, obstructing the accurate measurement of charge carrier mobilities. Here, a generally applicable method is presented to determine the true charge carrier mobility in an organic field-effect transistor (OFET). The method uses two additional finger-shaped gates that capacitively generate and probe an alternating current in the OFET channel. The time lag between drive and probe can directly be related to the mobility, as is shown experimentally and numerically. As the scheme does not require the injection or uptake of charges it is fundamentally insensitive to contact resistances. Particularly for ambipolar materials the true mobilities are found to be substantially larger than determined by conventional (direct current) schemes.     

最大熵迁移率谱分析的发展与应用

最大熵迁移率谱分析方法是用于研究和获得材料电学参数一种测试手段。它克服了传统的固定磁场霍尔测量方法的缺点,可以获得更多更准确的电学信息。本文介绍了最大熵迁移率谱分析方法的基本原理和特点,论述了最大熵迁移率谱分析方法的发展与应用,最后展望了最大熵迁移率谱分析方法的应用前景。     

腐蚀法制备绒面ZnO透明导电薄膜

利用中频脉冲磁控溅射系统制备高透过率、高电导率的平面ZnO薄膜。对平面ZnO薄膜进行短时间弱酸腐蚀,可以获得绒面效果的ZnO透明导电薄膜。分析了工作气压和衬底温度对薄膜绒面结构的影响,获得了适合薄膜太阳能电池的绒面ZnO透明导电薄膜。当压力控制在1.92Pa左右,衬底温度150～170℃范围内沉积的薄膜具有最佳的绒面和较低的电阻率,电阻率可达5.57×10-4Ω·cm,载流子浓度2.2×1020cm-3,霍尔迁移率40.1cm2/V·s,在可见光范围平均透过率超过85%。