Contacts at the Microelectronics Institute of Fudan University are: Gang Ruan, Professor, Director. Fax: +86-21-549-0323 Huang Yiping, Vice Director. Microelectronics Institute Fudan University INSTITUTE OF SEMICONDUCTORS, ACADEMIA SINICA, BEIJING Historical Background The Institute of Semiconductors is a multidisciplinary semiconductor research institute belonging to the Chinese Academy of Sciences. The Institute was established in 1960. The semiconductor division was the basis of the Institute of Physics, Chinese Academy of Sciences. At its inception, five research divisions were established that worked respectively on materials, devices, measurements and characterization, electronics and optoelectronics. The other three research groups worked in physics, chemical analysis, and thermoelectricity. Later, they were reorganized into seven research divisions and a pilot plant, the "109 plant," for fabrication of planar Si transistors. In 1964, a part of the optoelectronics division was transferred to the East China Research Institute of Technical Physics (now renamed "Shanghai Research Institute of Technical Physics") and the 109 plant became an independent plant under the Academy of Sciences. In the same year, work on integrated circuits began, and later the plant became organized into two research divisions that respectively worked on bipolar and MOS circuits. Very recently, a "Center of Microelectronics" has been created within the academy, based on the VLSI team of this institute and the 109 plant. The institute is located in the Haidian District of Beijing; it neighbors Tsinghua University to the west and the Beijing College of Forestry to the south. The institute occupies an area of about 87,000 m2 (about 22 acres). The main laboratory buildings include a seven-story materialand-device laboratory building, and a five-story physics-chemistry-electronics building, surrounded by the ion-beam laboratory, the clean room, the computer center, the library, and the general office building. The total laboratory floor space is about 30,000 m2. The institute also provides living quarters. The institute has made important contributions to the national development of semiconductor science and technology, and has undertaken many priority national projects. The Institute has also received many national and CAS awards for achievement. The honorary director and senior advisor of the institute is Professor Huang Kun, who spent 28 years as professor at the Peking University and about eight years as Director of the Institute of Semiconductors. He is one of four division members of the Chinese Academy of Sciences at the institute and continues an active role in science internationally, as well as in the research at the institute. The current director of the institute is Professor Wang Qiming. Organization of the Institute At the present time, the total number of personnel at the institute is about 1,000. The number of scientists and engineers with senior status is more than 100, and scientific personnel with intermediate and junior status is about 500. In recent years, the total number of scientists who have been abroad for a period of time for further studies or to carry out cooperative projects is above 60. Project groups form the basic units for carrying out scientific research, technological experiments, or developmental projects. The work of a project group is usually subdivided into a number of research tasks to be carried out. The project groups are organized into one division and nine laboratories as listed: Division of Semiconductor Laboratory of Semiconduct- - Laboratory of New Devices Laboratory of Sensors and - Laboratory of Microwave - Laboratory of Applied Elec- - Laboratory of Optoelectronic Devices - Laboratory of Physical and Chemical Analysis Laboratory for General Processing. In addition, the institute has an experimental device-processing factory and a number of supporting facilities, such as library, machine shop, and computer center. The editorial office also belongs to the institute. One of their major jobs is to edit the "Chinese Journal of Semiconductors," the major national journal on semiconductor science. Research Areas The following four research areas are currently active at the institute, 1. Semiconductor theory and basic physics 1981. Research work has included optical investigations and electronic transport at low temperature and high magnetic fields. Semiconductor surface physics. Surface and interface investigations with electron spectroscopy have been conducted on a number of topics, such as oxygen absorption and desorption on GaAs and Si surfaces, compositional effects at interfaces, the effects of defects and impurities on Schottky junctions, and problems relating to interfaces between a semiconductor and an oxide or ni This area includes the following tride film. six main topics: Solid-state theory, including lattice relaxation, multiphonon transitions, and theoretical calculation of various electronic structures. A theoretical multifrequency model has been developed to implement multiphonon transition calculations, and a statistical-distribution law has been established for the phonons emitted in multiphonon transitions. Electronic structure calculations have included development of theoretical methods as well as a wide range of applications, such as bulk band structures, deep centers, semiconductor surface, amorphous silicon, quantum wells, and superlattices. Physics of amorphous semiconductors presently focusing on the long-term stability of amorphous silicon under illumination, and the optoelectronic energy-conversion efficiency. On the basis of physical research, small area solar cells of amorphous silicon with a conversion efficiency of 9 % have been made. Physics of low-dimensional systems, a relatively new field of investigation at this institute. Research on the properties of a 2-D electron gas in metal oxide-semiconductor (MOS) structures and on modulation-doped heterojunctions was first started in Semiconductor spectroscopic research has been directed toward a wide range of scientific questions. Examples are photoluminescence under high pressure as a means of studying nitrogen-bound excitons in GaP or GaAs, or excitons in quantum wells. Raman spectra of disordered systems (mixed crystals and amorphous materials), and picosecond-spectroscopic investigation of the transient behavior of hot carriers in quantum wells. Physical problems closely related to junction lasers are investigated; for example, carrier losses and Auger processes in (In,Ga)(As,P) /InP double heterojunction lasers. Deep-level centers. Systematic investigations on the properties and behavior "4d impurities" in Si are carried out with various junctioncapacitance techniques. Also, nonmetallic elements (oxygen and carbon) in silicon are being investigated, bon) in silicon are being investigated, mainly in relation to their thermal-annealing behavior. 2. Semiconducting materials and related material physics Earlier, materials research at the Institute had focussed on the growth of perfect silicon single crystals. With the development of large-scale integration (LSI), technology in China, proper technology for the growth of silicon crystals with low-dislocation density, no swirl defect, and with uniform resistivity has been developed at the Institute. At present, work on silicon is mainly done on the investigation of micro defects and the so-called new donors, and on thermal annealing behavior. Currently, growth of semi-insulating GaAs and InP is also a priority subject for research. In the crystal pulling laboratory there are highpressure vessels that contain up to 100 atm overpressure of phosphorous for pulling InP, GaAs, or GaSb. Two-in. diameter InP crystals more than 4-in. long are routinely pulled with n, p, or intrinsic doping. The background impurity levels are as low as 5 x 1015 cm-3. (Five laboratories in China currently produce InP substrate material.) With the addition of Ga to the InP, the etch-pit count can be reduced from 5 x 104 to 1 - 5 × 103cm-2. Their current problem with both GaAs and InP substrate materials is learning to polish it satisfactorily for the demanding application in multiple quantum-well epitaxy, a problem that has been solved with GaSb. Single crystals of GaSb, 3-in. in diameter, are pulled routinely and are available for international sale. GaAs single crystals of 4-in. diameter are pulled, doped n, p, or intrinsic. The intrinsic GaAs is undoped and has a resistivity of 5 × 10' 0-cm. Epitaxial growth has always been one of the main topics of research in materials preparation. Work on silicon is directed toward developing new methods for low-temperature growth of high-quality epilayers. Heteroepitaxial growth is being pursued with silicon-on-sapphire (SOS) materials, related to the development of sensors and radiation-resistant ICs. Completely new modes of epitaxial growth are also being explored. Ultrathin-film growth is considered to be of great importance. The earliest effort of the Institute dates back to 1976, when the decision was made to design an MBE apparatus to be built in China. For several years up to now, good quality modulation-doped heterojunctions and superlattices have been grown. Efforts are being made to initiate research at an early date on metalorganic chemical-vapor deposition (MOCVD) growth. In the past few years, experimental research on MBE-grown quantum wells and superlattices has increased rapidly. Related device research has now begun. 3. Device research and device-physics research Device research at this institute includes optoelectronic devices, microwave devices, special integrated circuits (IC) and various sensors. This institute was among the earliest to start work on semiconductor epitaxial layers. Optical bistability and related device research has been a special problem under investigation at the institute for the past few years. As the result of research over the years, microwave oscillators and detectors that work at wavelengths of 4, 3, and 2 mm (150 GHz) have been developed successively and put to use. Research is now progressing towards submillimeter devices. Also, research is carried out on millimeterwave integrated circuits (MMICs), InP heterojunction devices, and the development of trapped plasma avalanche triggered transit (TRAPATT) oscillators with higher power and higher frequency. Recently work on high electron mobility transistors (HEMT) devices has also started. Special ICs are developed in research projects for further development of DYL circuits (an innovation achieved at this Institute) on the one hand and radiation-resistant CMOS circuits on the other hand. The institute did research on gas-sensitive sensors for a number of years and produced sensors for use in industry. More recently, research work has started on various types of sensors, including optical fiber thermal sensors, Hall-effect sensors, and ion-sensitive and biological enzymesensitive sensors. In recent years, extensive work has been done on the development of long-lifetime (Al,Ga)As/GaAs double-heterojunction lasers, lowthreshold (In, Ga) (As, P)/InP long-wave length double-heterojunction laser, (Al, Ga)As/GaAs doubleheterojunction power lasers, silicon PIN detectors, APD optoelectronic detectors, (In,Ga)As/InP long-wavelength PIN and ADP detectors, and a number of special junction-laser applications. Research has been conducted on basic physical problems 4. Semiconductor electronics relating to junction-laser behavior, e. g., output mode control, laser transient response, thermal characteristics, aging characteristics, and mechanism of failure. A group carrying out original theoretical research on computeraided design (CAD), relating to VLSI developed a few years ago, has proposed a new and advanced method for IC layout. Now, work is underway to implement their theoretical results for practical CAD applications. Historically research has been mainly directed toward instrumental application of semiconductor devices and advanced measuring instrument Huang Kun, Professor. Li Yuzhang, Associate Professor, Han He-Xiang, Associate Wang Youziang, Associated Zhuang Wanru, Professor, Head, Optoelectronic Devices Hsu Chen-Chia, Professor. Institute of Semiconductors, P.O. Box 912 Beijing, 100083, P.R. China After a preliminary stage of development centered on MBE growth apparatus and technology, research on semiconductor superlattices and microstructures was launched as a basic-research project of key priority at a national level in 1986. Significant progress has been achieved in the many fields, including theoretical and optical spectroscopy studies on electronic structures, lattice dynamics optical transitions, and energy relaxation of photo-excited electrons in superlattices and quantum wells; quantum transport and other electronic behavior of low-dimensional electronic systems; growth technologies and material characterization of MBE-grown superlattices and multilayered heterostructures; new electronic and optoelectronic devices based on superlattices and quantum wells. During this period, over 200 scientific papers have been published. On this basis, a new National Laboratory for Superlattices and Microstructures (NLSM) was estab lished on April 17, 1989 at the Insti tute of Semiconductors, Chinese Academy of Sciences. The motivation for the laboratory is to form a well equipped national research center in the field of semiconductor superlattices and microstructures. While technically based on the development and continuous refinement of MBE and MOCVD technologies, the main thrust of the laboratory is on basic physical research of new features of various low-dimensional systems, realized in semiconductor superlattices and multilayered microstructures, and their potential for applications in electronics, optoelectronics, and photonics. Scope of the Scientific Program The main fields of investigation covered at the laboratory are as follows: Theoretical studies on electronic structures, elementary excitations and interaction processes, as well as transport properties in low-dimensional semiconductor structures. - Spectroscopic investigations, including conventional and time-resolved photoabsorption and photoreflection spectroscopies, Raman spectroscopy and magneto-optic spectroscopies used in combination with temperature, pressure, and electric- or magneticfield modulation techniques. Research topics consist of energy band structures, intrinsic and extrinsic recombinations, dynamics of photo-excited electrons and nonlinear optical properties in semiconductor superlattices and quantum wells. Quantum transport (parallel and perpendicular to inter faces) and their relevance to dimensional size and underlying physical processes. Investigation of electronic properties and behaviors of impurities, defects and deeplevel centers related to MBE- and MOCVD-grown materials. - Material growth and the technologies of various low-dimensional semiconductor structures with artificially tailored band structures. Physical studies of processes underlying superlattice- or quantum-well-based devices. tor superlattices, metal-semiconductor interfaces, transition-metal surfaces and interfaces, studies of single and multilayer thin films, and adsorption of gas on solid surfaces. The NLSP research programs fall under five main headings. High-T, Superconductive Thin-Film Research The composition, valence electron state, band structure, oxygen deficiency, temperature dependence, and element substitution of high T Surface and interface studies of superconductors have been studied new materials Research studies are conducted on the surfaces and interfaces of varied materials. The formation and behavior of interfaces are studied in detail by surface techniques at the atomic scale. The behavior of interfaces is quite different because of the differences in preparation technology and the materials that form interfaces. The physical and chemical properties of interface are investigated to provide the basic theory and a model to solve problems in practical interfaces such as interfaces in multilayers of semiconductor devices, and the composite materials of heterogeneous catalysts. Surface theory The proposed jellium-slab model is used with the linearized augmented-plane-wave (LAPW) method for energy-band calculations to investigate compositions, structures, and electronic states of clean and absorbed surfaces of metals, semiconductors and their compounds. Meanwhile, the ASED-molecular orbital method is used to discern the relation between charge transfer and coverage in the complex coadsorption systems. Also in connection with MBE growth of semiconductor multilayer thin-film materials, we have studied the interface stability, electronic structure, and local states and diffusion process of intrinsic defects. A structure of a photo-electric device with tunable superlattice energy gap with varying period is proposed. c by surface photoemission electron spectroscopy and energy-loss spectroscopy. The relationship of the valence-electron states, band structure, and oxygen deficiency of the various atoms in the high T, superconductors with superconducting characteristics has been investigated. All these have provided strong experimental evidences for the understanding of mechanisms of high-T, superconductivity. After having prepared the YBaCuO superconducting thin films by thus electron-beam evaporation, achieving zero resistance at liquid nitrogen temperature first time in China, BiSrCaCuO superconducting films have been fabricated by laser ablation. The field and temperature dependence of critical current of YBaCuO thin films, J(H) and J(T), have been measured. Critical current Jc, was found out, was restricted by the weak link network between the grains in the films. The negative magneto resistance phenomena were obscured in low fields, which could be used in high-T superconducting devices. The metal-superconductor interface, interface chemistry, interface distribution, and interface diffusion have been studied systematically. Some of the research studies were awarded first prize at the national natural science in 1989. In cooperation with the Royal Institute of Technology of Sweden, the Y-and Bibased superconducting thin films were fabricated by a special on-axis sputtering method with a stoichiometric target. |