氮化物半导体电子器件的若干研究进展

近年来,氮化物半导体电子器件和材料研究有了重大的进展。在国家自然科学基金资助下,西安电子科技大学、北京大学和中科院微电子所完成了国家自然科学基金重点项目《GaN宽禁带微电子材料和器件重大基础问题研究》。致力于通过氮化物电子材料和器件的基础物理机理研究提高GaN电子材料的结晶质量和电学性能、发展新结构GaN异质结材料研究,获得高性能的GaN HEMT微波功率器件。本文主要介绍该项目在GaN微波功率HEMT和新型高k栅介质MOS-HEMT、InAlN/GaN材料的生长和物性缺陷分析以及HEMT器件研制、GaN异质结的量子输运和自旋性质研究以及GaN材料高场输运性质和耿氏器件等几个方面取得的研究进展。     

Progress in Group Ⅲ nitride semiconductor electronic devices

Recently there has been a rapid domestic development in groupⅢnitride semiconductor electronic materials and devices.This paper reviews the important progress in GaN-based wide bandgap microelectronic materials and devices in the Key Program of the National Natural Science Foundation of China,which focuses on the research of the fundamental physical mechanisms of group III nitride semiconductor electronic materials and devices with the aim to enhance the crystal quality and electric performance of GaN-based electronic materials, develop new GaN heterostructures,and eventually achieve high performance GaN microwave power devices.Some remarkable progresses achieved in the program will be introduced,including those in GaN high electron mobility transistors(HEMTs) and metal-oxide-semiconductor high electron mobility transistors(MOSHEMTs) with novel high-k gate insulators,and material growth,defect analysis and material properties of InAlN/GaN heterostructures and HEMT fabrication,and quantum transport and spintronic properties of GaN-based heterostructures,and highelectric -field electron transport properties of GaN material and GaN Gunn devices used in terahertz sources.     

Recent Progress on Synthesis,Intrinsic Properties and Optoelectronic Applications of Perovskite Single Crystals

Metal halide perovskite have shown great potential for applications in photovoltaics, light-emitting diodes and photon detectors, mainly owing to their superb optoelectronic properties, low-cost raw materials and facile fabrication process. Although, polycrystalline perovskite thin-films have been actively investigated for preparing various optoelectronic devices, the presence of detrimental defects at grain boundaries, serious ion migration and limited stability unfortunately hinder their device performance and practical application. As a contrast, perovskite single crystals (SCs) exhibit no grain boundaries, much lower trap density and much improved stability, hence providing a more attractive choice for not only optoelectronic device applications but also fundamental research. In this review, recent progress in the growth methods of perovskite SCs is summarized, followed by giving a detailed introduction of the intrinsic properties of perovskite SCs including optical properties, defects, charge carrier dynamics, ion migration and stability. On these base, the applications of perovskite SCs in various optoelectronic devices like solar cells, photodetectors, and radiation detectors are discussed, where the relationship between the composition, device architecture and device performance is highlighted. Finally, a tentative discussion on the current challenges and future opportunities in the development of perovskite SCs and optoelectronic devices is presented.     

Recent developments in monolithic integration of InGaAsP/InP optoelectronic devices

Monolithically integrated optoelectronic circuits combine optical devices such as light sources (injection lasers and light emitting diodes) and optical detectors with solid-state semiconductor devices such as field effect transistors, bipolar transistors, and others on a single semiconductor crystal. Here we review some of the integrated circuits that have been realized and discuss the laser structures suited for integration with emphasis on the InGaAsP/InP material system. Some results of high frequency modulation and performance of integrated devices are discussed.     

Emerging gallium nitride based devices

Wide bandgap GaN has long been sought for its applications to blue and UV emitters and high temperature/high power electronic devices. Recent introduction of commercial blue and blue-green LED's have led to a plethora of activity in all three continents into the heterostructures based on GaN and its alloys with AlN and InN. In this review, the status and future prospects of emerging wide bandgap gallium nitride semiconductor devices are discussed. Recent successes in p-doping of GaN and its alloys with InN and AlN, and in n-doping with much reduced background concentrations have paved the way for the design, fabrication, and characterization of devices such as MESFET's, MISFET's, HBT's, LED's, and optically pumped lasers. We discuss the electrical properties of these devices and their drawbacks followed by future prospects. After a short elucidation of materials characteristics of the nitrides, we explore their electrical transport properties in detail. Recent progress in processing such as formation of low-resistance ohmic contacts and etching is also presented. The promising features of quarternaries and double heterostructures in relation to possible current injection lasers, LED's, and photodetectors are also elaborated on     

A metal-insulator-silicon junction seal

Most semiconductor devices today have a costly vacuum-tight encapsulation that provides a microenvironment for high reliability and electrical connections to the circuit in which it is used. A junction seal consisting of a metal-insulator-silicon (MIS) system of materials has been developed to replace the vacuum-tight encapsulation. The MIS junction seal, consisting of platinum silicide-titanium-platinum-gold contacts and a Silicon nitride overcoat, provides the necessary encapsulation for high reliability. Electrical and mechanical connections are provided by gold beam-deads. During fabrication, the contact windows are opened in the deposited silicon nitride layer either by etching with boiling phosphoric acid using SiO2as a mask or by anodically converting the silicon nitride in the windows to a soluble oxide. The multilayer contact is then applied to complete the junction seal. The initial characteristics of sealed-junction transistors fabricated by the above methods were similar to those of the unsealed transistors. The reliability of the sealed-junction transistors determined by accelerated aging after an intentional sodium contaminafion of 10¹⁷atoms/cm²surpassed that of the standard silicon planar transistors sealed in a vacuum-tight enclosure.     

Research progress of Si-based germanium materials and devices

Si-based germanium is considered to be a promising platform for the integration of electronic and photonic devices due to its high carrier mobility, good optical properties, and compatibility with Si CMOS technology. However, some great challenges have to be confronted, such as: (1) the nature of indirect band gap of Ge; (2) the epitaxy of dislocation-free Ge layers on Si substrate; and (3) the immature technology for Ge devices. The aim of this paper is to give a review of the recent progress made in the field of epitaxy and optical properties of Ge heterostructures on Si substrate, as well as some key technologies on Ge devices. High crystal quality Ge epilayers, as well as Ge/SiGe multiple quantum wells with high Ge content, were successfully grown on Si substrate with a low-temperature Ge buffer layer. A local Ge condensation technique was proposed to prepare germanium-on-insulator (GOI) materials with high tensile strain for enhanced Ge direct band photoluminescence. The advances in formation of Ge n⁺p shallow junctions and the modulation of Schottky barrier height of metal/Ge contacts were a significant progress in Ge technology. Finally, the progress of Si-based Ge light emitters, photodetectors, and MOSFETs was briefly introduced. These results show that Si-based Ge heterostructure materials are promising for use in the next-generation of integrated circuits and optoelectronic circuits.     

n型GaN欧姆接触的研究进展

Ⅲ-Ⅴ族GaN基材料以其在紫外光子探测器、发光二极管、高温及大功率电子器件等方面的应用潜能而被广为研究.其中,低阻欧姆接触是提高GaN基器件光电性能的关键.金属/GaN界面上较大的欧姆接触电阻一直是影响器件性能及可靠性的一个问题.对于各种应用来说, GaN的欧姆接触需要得到改进.通过对相关文献的归纳分析,本文主要介绍了近年来在改进n-GaN工艺,提高欧姆接触性能等方面的研究进展.     

Recent advances in optoelectronic properties and applications of two-dimensional metal chalcogenides

Since two-dimensional (2D) graphene was fabricated successfully, many kinds of graphene-like 2D materials have attracted extensive attention. Among them, the studies of 2D metal chalcogenides have become the focus of intense research due to their unique physical properties and promising applications. Here, we review significant recent advances in optoelectronic properties and applications of 2D metal chalcogenides. This review highlights the recent progress of synthesis, characterization and isolation of single and few layer metal chalcogenides nanosheets. Moreover, we also focus on the recent important progress of electronic, optical properties and optoelectronic devices of 2D metal chalcogenides. Additionally, the theoretical model and understanding on the band structures, optical properties and related physical mechanism are also reviewed. Finally, we give some personal perspectives on potential research problems in the optoelectronic characteristics of 2D metal chalcogenides and related device applications.     

SiC电力电子器件研究现状及新进展

由于硅材料本身的限制,传统硅电力电子器件性能已经接近其极限,碳化硅(SiC)器件的高功率、高效率、耐高温、抗辐照等优势逐渐突显,成为电力电子器件一个新的发展方向.综述了SiC材料、SiC电力电子器件、SiC模块及关键工艺的研究现状,重点从材料、器件结构、制备工艺等方面阐述了SiC二极管、金属氧化物半导体场效应晶体管(MOSFET)、结晶型场效应晶体管(JFET)、双极结型晶体管(BJT)、绝缘栅双极晶体管(IGBT)及模块的研究进展.概述了SiC材料、SiC电力电子器件及模块的商品化情况,最后对SiC材料及器件的发展趋势进行了展望.     

碳纳米管在典型微纳电子器件中的应用进展

优异的电学、热学、机械特性和化学稳定性以及独特的一维纳米结构,使碳纳米管(CNT)成为应用在微纳电子器件中的理想功能材料。与传统电子器件相比,CNT微纳电子器件性能更为优异。本文综述了近年来制备和改进基于CNT的场发射器、晶体管和传感器的研究进展。经过特定方法的组装和处理,可使CNT场发射器获得低阀值电压、高发射电流和发射电流稳定等优异性能,使CNT晶体管具有高迁移率、大跨导和大电流开闭比,可提高各种CNT传感器的灵敏度。     

Oxide-based thin film transistors for flexible electronics

The continuous progress in thin film materials and devices has greatly promoted the development in the field of flexible electronics.As one of the most common thin film devices,thin film transistors (TFTs) are significant building blocks for flexible platforms.Flexible oxide-based TFTs are well compatible with flexible electronic systems due to low process temperature,high carrier mobility,and good uniformity.The present article is a review of the recent progress and major trends in the field of flexible oxide-based thin film transistors.First,an introduction of flexible electronics and flexible oxide-based thin film transistors is given.Next,we introduce oxide semiconductor materials and various flexible oxide-based TFTs classified by substrate materials including polymer plastics,paper sheets,metal foils,and flexible thin glass.Afterwards,applications of flexible oxide-based TFTs including bendable sensors,memories,circuits,and displays are presented.Finally,we give conclusions and a prospect for possible development trends.     

Charge carrier recombination and generation analysis in materials and devices by electron and optical beam microscopy

Electron beam induced current (EBIC) and optical beam induced current (OBIC) methods of scanning microscopy are here described in view of their applications in the analysis of recombination and generation of carriers in devices and materials. These analyses allow to evidence peculiarities in the charge carriers transport and/or failure in devices charge collection, measuring electrical parameters in the micrometer range, such as potential distribution within the sample, diffusion length and surface recombination velocity. This review will illustrate some case studies relevant to devices and material investigations in the two geometrical configurations: normal and planar. Literature results are reviewed in order to show capabilities and effectiveness of these methods in the investigation of the defect electrical activity and resulting localized minority carrier recombination and generation in devices under operating conditions, as well as in native semiconductor materials such as silicon, gallium arsenide and gallium nitride.     

Silicon-based semiconductor heterostructures: column IV bandgapengineering

The use of strained layer epitaxy to grow high-quality Ge_x Si_1-x/Si heterostructures and their application to a wide range of heterostructure devices are addressed. The author reviews the mechanisms of strained layer growth, the bandstructure of the resulting material, and its use in test devices, including superlattice avalanche photodiodes for fiber optic communication, intrasubband optical detectors and arrays operating in the 10-15 μm wavelength range, mobility enhanced modulation-doped transistors, heterojunction bipolar transistors with cutoff frequencies of 75 GHz, and negative resistance devices based on resonant tunneling and real-space carrier transfer     

InP基应变自组装纳米材料及其光电子器件研究进展

半导体低维结构材料,如量子线(点)材料,由于其特殊的电子结构,在新一代光电子、微电子器件中有着重要的应用价值。本文对应变自组装InP基量子线(点)材料的生长制备、光学和电学特性及其在半导体激光器、红外探测器及其他光电子和微电子器件中的应用进行了综述,指出了目前需要改进的一些方面,并提出了一些相应的解决途径。     

Field-effect transistor memories based on ferroelectric polymers

Field-effect transistors based on ferroelectrics have attracted intensive interests, because of their non-volatile data retention, rewritability, and non-destructive read-out. In particular, polymeric materials that possess ferroelectric properties are promising for the fabrications of memory devices with high performance, low cost, and large-area manufacturing, by virtue of their good solubility, low-temperature processability, and good chemical stability. In this review, we discuss the material characteristics of ferroelectric polymers, providing an update on the current development of ferroelectric field-effect transistors (Fe-FETs) in non-volatile memory applications.     

Heterostructure devices using self-aligned p-type diffused ohmiccontacts

Describes the use of a p-type refractory ohmic contact in ohmic self-aligned devices. The contacts are based on self-aligned diffusion of zinc-doped tungsten film. The diffusion is nearly isotropic in the vicinity of silicon nitride sidewalls, allowing self-alignment of ohmic contacts with emitters and gates. Low-resistance contacts (<10^-6 Ω·cm²) are formed both to GaAs and GaAlAs, and the lifetime of the diffused region is superior to that obtained from implantation. Heterostructure bipolar transistors (HBTs) showing high current gains (⩾50 at 2×10³ A·cm^-2 and ⩾200 at 1×10⁵ A·cm^-2 with micrometer-sized emitter widths) and p-channel GaAs gate heterostructure field-effect transistors (HFETs) showing high transconductances (78 mS/mm at 2.2-μm gate length) have been fabricated using this contact     

Organic Synaptic Transistors: The Evolutionary Path from Memory Cells to the Application of Artificial Neural Networks

The progress of neural synaptic devices is experiencing an era of explosive growth. Given that the traditional storage system has yet to overcome the von Neumann bottleneck, it is critical to develop hardware with bioinspired information processing functions and lower power consumption. Transistors based on 2D materials, metal oxides, and organic materials have been adopted to mimic the synapse of a human brain, due to their high plasticity, parallel computing, integrated storage, and system information processing. Among these materials used to build transistors, organic semiconductors are considered to be the most promising candidate for neural synaptic devices and bio-electronics, owing to their easy processing, mechanical flexibility, low cost, good bio-compatibility, and ductility. This review focuses on the recent advances in organic synaptic devices with various structures, materials, and working mechanisms. The applications of artificial neural networks that integrate multiple organic synaptic transistors are also concretely discussed. Finally, the challenges that organic synaptic devices currently face are discussed and future developments are forecast.     

Nonvolatile Floating‐Gate Memories Based on Stacked Black Phosphorus–Boron Nitride–MoS2 Heterostructures

Research on van der Waals heterostructures based on stacked 2D atomic crystals is intense due to their prominent properties and potential applications for flexible transparent electronics and optoelectronics. Here, nonvolatile memory devices based on floating‐gate field‐effect transistors that are stacked with 2D materials are reported, where few‐layer black phosphorus acts as channel layer, hexagonal boron nitride as tunnel barrier layer, and MoS₂ as charge trapping layer. Because of the ambipolar behavior of black phosphorus, electrons and holes can be stored in the MoS₂ charge trapping layer. The heterostructures exhibit remarkable erase/program ratio and endurance performance, and can be developed for high‐performance type‐switching memories and reconfigurable inverter logic circuits, indicating that it is promising for application in memory devices completely based on 2D atomic crystals.     

On the Substrate Thermal Optimization in SiC-Based Backside-Mounted High-Power GaN FETs

This paper presents a discussion on the substrate thermal design of backside-mounted power GaN high-electron mobility transistors. After a review on the thermal properties of the relevant materials and their temperature dependences, design guidelines are proposed on the basis of 3-D thermal simulations; the results presented suggest that in SiC-based devices, substrate thinning does not typically improve the thermal resistance or the dynamic thermal behavior. Contrary to what happens in III-V GaAs- or InP-based discrete or integrated devices, therefore, microstrip design on a thinned substrate (as opposed to coplanar design on a comparatively thick substrate) is generally not thermally superior. This should make possible, from the thermal standpoint, the realization of coplanar multifunctional GaN-based monolithic microwave integrated circuits integrating, e.g., low-noise and power stages and avoiding the use of via holes.