Controlling the crystal formation in solution-process for organic field-effect transistors with high-performance

We control the growth of high-quality organic semiconducting crystals in the aim of transistor application. By finely tuning the processing parameters, both isolated crystals showing characteristic facet angles and irregular-shaped, thin crystalline domains are obtained in large sizes (>400 μm). Structural investigations indicate that the various shapes of crystals are in the same crystal structure, and reveal that the irregular-shaped crystalline domains are composed by terrace of molecularly flat regions, which can be up to hundreds of microns in size. When applied in field-effect transistors, the thin crystalline domains exhibit the best performance showing μ_FET up to 4.4 cm²/V s. This is an order of magnitude higher than that of the transistors made from as-spun films and thick crystals. The approach well demonstrates the importance of fine control of crystal formation and can be generally used for getting organic crystal transistors.     

掺砷多晶硅在微波晶体管中的应用

报道了用低压化学汽相淀积生长掺砷多晶硅的实验结果。应用掺砷多晶硅作发射板材料，研制出Ｃ波段连续波输出功率大于３Ｗ的晶体管和Ｌ，Ｐ波段１００Ｗ的脉冲功率晶体管。     

Intralayer vs. interlayer electronic coupling in perylene imide thin films

Optical absorption spectroscopy was performed on thin films of the perylene imide dye PDI8-CN2 during film growth by physical vapor deposition. The spectra showed an energy shift of 40 meV for the lowest energy transition with increasing film thickness from a sub-monolayer thickness regime to about 40 nm average film thickness with a clear step indicating the complete formation of the first monolayer. To analyze the observed characteristics a model was developed which is based on different contributions of transition dipole coupling in different crystalline directions. Clear dominance of intralayer coupling in the a–b crystal plane was found whereas interlayer coupling was found to be negligible. This was rationalized by the presence of alkyl chains as a spacer between the aromatic cores oriented along the c-direction. Atomic force microscopy of the films revealed layer-by-layer growth for the first monolayers and confirmed a texture with the c-axis perpendicular to the surface. The growth mode was correlated with the extent of intermolecular coupling in the different crystalline directions. We will discuss perspectives to optimize electron transport in PDI8-CN2 thin films which have been proposed as molecular semiconductor in organic field effect transistors (OFET).     

GaAlAs／GaAsHBT的现状和应用展望

本文评述了GaAlAs/GaAs HBT的研究现状,着重讨论了制造HBT的重要技术和应用前景;对HBT的进一步发展也进行了探讨。     

硅低温低频低噪声双极晶体管的分析与设计

对硅双极晶体管低频噪声的本征与非本征两种分量进行了系统的理论分析，并研究了各自的温度特性，在此基础上，设计并研制出一种多晶硅发射极低温低频低噪声晶体管，其等效输入噪声电压。     

Effective mobility in amorphous organic transistors: Influence of the width of the density of states

The temperature dependence of poly(3-hexylthiophene-2,5-diyl) (P3HT)/polystyrene (PS) blend organic transistor current/voltage (I–V) characteristics has been experimentally and theoretically studied. The planar transistors, realized by drop casting the P3HT/PS ink, exhibit high mobilities (over 5 × 10⁻³ cm² V⁻¹ s⁻¹) and good overall characteristics. A transistor model accounting for transport mechanisms in disordered organic materials was used to fit the measured characteristics. Using a single set of parameters, the measured effective mobility versus gate bias, either increasing or decreasing with the gate bias depending on temperature, is well reproduced over a wide temperature range (130–343 K). A Gaussian density of states width of 0.045 eV was determined for this P3HT/PS blend. The transistor I–V characteristics are very well described considering disordered material properties within a self-consistent transistor model.     

高截止频率异质结双极晶体管的研制

本文介绍了研制异质结双极晶体管(HBT)的工艺过程。使用MOCVD生长的GaAlAs/GaAs多层结构外延材料,采用离子注入隔离和湿法腐蚀技术,实现基极与发射极台面自对准工艺,研制出截止频率为22GHz的HBT。     

L波段150W宽带硅脉冲功率晶体管

设计了一种称之为多晶硅覆盖树技状结构的双极型微波功率晶体管。该器件采用掺砷多晶硅发射极，同时具备有覆盖和树枝状两种图形结构的优点。器件引入扩散电阻和分布式多晶硅电阻组合而成的发射极复合镇流电阻，实现对发射极电流二次镇流，器件表现出良好的微波性能和高的可靠性。经内匹配，在L波段脉冲输出大于100W（36V），脉宽150μs，工作比10％，增益大于7．5dB，效率大于45％，器件最大输出达150W（42V）。     

双极型压控晶体管模型及原理

本文提出一种新的双极型压控晶体管模型，并说明其工作原理。这种器件有两种载流子参与导电，有较大的电流密度和功率，导电能力又受电压控制，具有较大的输入阻抗，兼有双极器件和MOS场效应器件的特点。     

Molecular heterostructure devices composed of langmuir-blodgett films of conducting polymers

Organic heterostructures have been fabricated by alternating the deposition of monoand multilayers of undoped poly(3-hexylthiophene) and doped polypyrrole prepared by the Langmuir-Blodgett technique. The dopant profiles of the structures have been electrically characterized by incorporating the polymer layers as the active semiconductive material into metal-insulator-semiconductor and Schottky barrier device configurations. The dopant concentrations were evaluated by capacitance-voltage measurements. The results indicate modulated dopant profiles and a possible transfer of dopants. The dopant concentrations differ by about an order of magnitude between the undoped and doped layers. The Schottky barriers become thinner the closer the doped polypyrrole monolayer lies to the Schottky electrode.     

硅双极型高速工艺和与其相容的硅PIN探测器

文章描述硅双极高速工艺，和一种能与双极工艺相容的硅ＰＩＮ探测器的结构及设计，从而提出一套易于实现两者集成的相容工艺。研制的单片集成光接收机，其中硅ＰＩＮ探测器的光电响应为０．４３Ａ／Ｗ，整机的响应度为４．４×１０３Ｖ／Ｗ，工作频率２５０ＭＨｚ。     

Controlling of electronic parameters of GaAs Schottky diode by poly(3,4-ethylenedioxithiophene)-block-poly(ethylene glycol) organic interlayer

The electronic properties of metal-organic semiconductor-inorganic semiconductor structure between GaAs and poly(3,4-ethylenedioxithiophene)-block-poly(ethylene glycol) organic film have been investigated via current-voltage and capacitance-voltage methods. The Au/PEDOT/n-GaAs contact exhibits a rectification behavior with the barrier height of 0.69 eV and ideality factor value of 3.94. The barrier height of the studied diode (0.67 eV) is lower than that of Ni/n-GaAs/In (0.85 eV) and Au/n-GaAs/In Schottky diodes. The decrease in barrier height of Au/n-GaAs/In Schottky diode is likely to be due to the variation in the space charge region in the GaAs. The obtained results indicate that control of the interfacial potential barrier for metal/n-GaAs diode was achieved using thin interlayer of the poly(3,4-ethylenedioxithiophene)-block-poly(ethylene glycol).     

InGaAsP/InP准平面异质结双极晶体管及其与光器件的集成

本文采用计算机辅助分析等方法,讨论了InGaAs/InP异质结双极晶体管(HBT)结构参数与其性能的关系.在此基础上,提出了一种准平面、双集电区HBT,及其相应的制作工艺.初步测试了器件的性能,就其与材料质量的关系作了讨论.文章还提出和制作了一种采用这种HBT为电子器件的光电子集成电路(OEIC).     

PNP和NPN型异质结双极晶体管的不同设计考虑

PNP和NPN高频异质结双极晶体管的设计有明显不同，这主要归因于砷化镓中电子与空穴的迁移率存在显著差别。这种差别在基区和子集电区外延层的设计中体现得尤为明显。文中详细讨论了PNP和NPN两种类型的异质结双极晶体管各自外延层的设计考虑。     

Modulation of the magnetic properties in zigzag-edge graphene nanoribbons by connection sites

Based on the first-principles method, the magnetic properties for zigzag–edge graphene nanoribbon (ZGNR) junctions are investigated. The results show the system had the ferromagnetic or antiferromagnetic ground state depending on the connection sites between ZGNR electrodes and the central ZGNR. The junction displays a metallic behavior when the central ZGNR is connected at the middle site of electrodes with a ferromagnetic state, but shows obvious spin semiconductor feature when the connection site is shifted to the edge of the ZGNR. For the antiferromagnetic states, all models show a semiconductor behavior, which originates from the spin-degenerate edge states. While for the antiparallel spin configuration, the spin density of the central ribbon is affected by connection sites, and it shows weaker little by little with the central ribbon moving from bottom to the middle site, which is different obviously from ferromagnetic or antiferromagnetic state. When one edge state of the central ZGNR is broken, bipolar spin semiconductor features can be obtained with different band gaps at suitable connection sites.     

光控功率开关BMFET的特性分析与数值模拟

讨论了光驱动ＢＭＦＥＴ作为光控功率开关的工作原理，根据理论分析和计算机模拟讨论了器件结构参数和外加偏置电路与工作特性的关系，为器件优化设计提供依据。     

Electrical and photovoltaic properties of a n-Si/chitosan/Ag photodiode

The electrical and photovoltaic properties of AuSb/n-Si/chitosan/Ag diode have been investigated. The ideality factor, barrier height and Richardson constant values of the diode at room temperature were found to be 1.91, 0.88 eV and 121.4 A/cm² K², respectively. The ideality factor of the diode is higher than unity, suggesting that the diode shows a non-ideal behaviour due to series resistance and barrier height inhomogeneities. The barrier height and ideality factor values of Ag/CHT/n-Si diode at room temperature are significantly larger than that of the conventional Ag/n-Si Schottky diode. The φ_B value obtained from C-V measurement is higher than that of φ_B value obtained from I-V measurement. The discrepancy between φ_B(C-V) and φ_B(I-V) barrier height values can be explained by Schottky barrier height inhomogeneities. AuSb/n-Si/chitosan/Ag diode indicates a photovoltaic behaviour with open circuit voltage (V_oc = 0.23 V) and short-circuit current density (J_sc = 0.10 μA/cm⁻²) values.     

突变异质结双极晶体管中的复合效应与电流传输

建立了带有不掺杂隔离层的突变异质结双极晶体管（ＨＢＴ）模型，在热场发射－扩散（ＴＦＤ）理论的基础上，又考虑了空间电荷区中的复合效应。对ＡｌＧａＡｓ／ＧａＡｓＨＢＴ特性的分析表明，不掺杂隔离层虽可有效地降低导带边的势垒尖峰，提高发射结的注入效率，但也会增大空间电荷区中的复合电流。因此，在实际器件的设计和制作中，应适当选择不掺杂隔离层的厚度，以获得较好的器件特性。还给出了计算突变异质结界面处电子准费米能级不连续的公式。     

Interface electronic structure between organic semiconductor film and electrode metal probed by photoelectron yield spectroscopy

We present an investigation of the interface between organic semiconductor films and metal substrates (organic/metal interface) using photoelectron yield spectroscopy (PYS) as the probing technique. PYS studies were conducted on the pentacene/Au, copper phthalocyanine (CuPc)/Au, and perfluorinated zinc phthalocyanine (F₁₆ZnPc)/Au, and the results were compared with literature results obtained using conventional ultraviolet photoemission spectroscopy (UPS). PYS is advantageous for probing the electronic structure of the organic/metal interface because of the relatively long mean free path of photoexcited electrons with very low kinetic energy in PYS, which enables the detection of the photoelectrons from the metal substrate buried deep in the organic film. We demonstrate herein that the use of PYS reduces the significance of the final state effect of the electronic density surrounding the photohole at the organic molecule generated after the photoemission; this effect is known as the electric polarization effect. Although this effect has a significant influence on the results obtained using conventional UPS, the reduced influence of the final state effect in PYS makes it possible to construct an energy level diagram at the organic/metal interface with greater accuracy than can be achieved with UPS. In addition, a novel mechanism of the photoelectron detection for PYS enables us to apply PYS to very thick organic films, and therefore, PYS provides a reliable value of ionization energy for organic films without the influence of the substrate.Because the interface electronic structure has a significant influence on the carrier injection properties of organic devices, the increased reliability of the information obtained by PYS will render it very useful for the improvement of device performance as well for understanding their operation principles.     

Degenerate cadmium oxide films for electronic devices

Highly conducting and transparent cadmium oxide films have been deposited on Corning 7059 glass substrates by ion-beam sputtering and by spray pyrolysis. The electrical and optical properties of CdO films prepared by the two techniques are similar. Typical films of 0.5 μm thickness have electrical resistivities of (2–5) × 10^-3 ohm-cm, carrier concentrations of approximately 10²⁰ cm^-3, and an optical transmission of higher than 70% in the wavelength range of 600–900 nm. An optical bandgap of 2.4–2.42 eV was deduced from the optical transmission data.