Picosecond Integrated Circuits in Germanium and Silicon

Recent advances in semiconductor technology make possible a planar technology for germanium similar to that used for silicon integrated circuits. Calculations based upon material properties indicate a considerable advantage to germanium over silicon for high-speed logic-switching applications.This is due largely to the better electron and hole mobilities for germanium. Switching circuit delays have been measured in both germanium and siliconin hybrid and integrated circuit form. For a given level of device sophistication (measured in terms of the stripe widths used on the devices) the germanium circuits are about three times faster than the equivalent silicon circuits.     

硅光子器件及其集成技术的研究

主要探讨了偏振分集光路、可调光衰减器、波导耦合型锗光电探测器等硅光器件的研究进展,分析了其结构及技术参数,随后探讨了VOA-PD单片集成技术以及VMUX单片集成技术两种硅基单片集成技术,指出硅光子器件的性能指标已经能满足现代光纤通信系统的要求。     

Platinum and Rhodium Silicide–Germanide Optoelectronics

Since the introduction of SiO₂/Si devices in the 1960s, the only basic change in the design of a MOSFET has been in the gate length. The channel thickness has fundamentally remained unchanged, as the inversion layer in a silicon MOSFET is still about 10 nm thick. Bipolar transistor base widths have been of sub-micron dimensions all this time. It is time for a new property to be exploited in concert with the high mobility strained-silicon channels and silicon–germanium alloys. This property is the inherently low parasitic series resistance of Schottky barrier contacts. Schottky contacts, beam leads, and microbridges, while originally developed in silicon, have been successfully integrated into compound semiconductors for optoelectronics. Reintroduction of these technologies in optoelectronics based on silicon–germanium is proposed. Several new applications using platinum and rhodium compounds of silicon and germanium are presented.     

Study on the RF Sputtered hydrogenated amorphous silicon–germanium thin films

In this study mechanical and electrical properties of the RF sputtered hydrogenated amorphous silicon germanium thin films deposited at room temperature have been discussed. Interesting correlation between the resistance and the flow of hydrogen is observed. Further, both band and hopping conduction mechanisms are found to exist simultaneously for the studied amorphous silicon germanium films.     

First-principles study of the lattice integration of palladium defects in doped germanium and silicon

Time-differential perturbed angular correlations spectroscopy of palladium in doped germanium has identified palladium-vacancy pairing in n-type antimony-doped, p-type gallium-doped and undoped germanium. In contrast, an equivalent study of palladium defects in doped silicon suggests a different scenario for the silicon host. Palladium-vacancy pairing has been proposed in n-type silicon irrespective of the dopant type (phosphorous, arsenic or antimony) but palladium–boron pairing has been speculated to occur in p-type boron-doped silicon. This thus raises the question: why does palladium pair with a dopant atom in p-type silicon, but with a vacancy in p-type germanium? Based on the density functional theory calculations carried out in this work, it is suggested that the size of the dopant and the host material both play a crucial role in determining the type of palladium-defect complex that is formed. The calculations predict a configuration with the palladium atom on a bond-centered interstitial site pairing with a semi-vacancy on either side in gallium-doped and antimony-doped silicon and germanium, respectively. Whereas, a configuration with the palladium atom on a bond-centered interstitial site pairing with the dopant was proposed in boron-doped silicon and germanium. In further support of the argument, in n-type phosphorous-doped materials the calculations predict a configuration with the palladium atom on a bond-centered interstitial site pairing with a semi-vacancy on either side in silicon, but a configuration with the palladium atom on a bond-centered interstitial site pairing with the phosphorous dopant in germanium.     

SiGe: a key to unlocking the potential of solar cells

Research and development of silicon germanium (SiGe) has been under way for well over a decade. A surprising number of research institutes have been developing photovoltaic devices based on the SiGe alloy system for almost as long. While the technology is still some way off making a full-scale commercial impact, its capability remains as impressive as ever. SiGe stands as a highly promising means to unlock the fullest potential of thin-film silicon photovoltaics.     

Selective chemical etching of polycrystalline SiGe alloys with respect to Si and SiO2

Polycrystalline SiGe etches that are selective to silicon dioxide as well as silicon are needed for flexibility in device fabrication. A solution of NH₄OH, H₂O₂, and H₂O has been found to selectivity etch polycrystalline silicon-germanium alloys over both silicon and silicon dioxide. Optimum composition of the solution was determined by maximizing etch rates for SiGe films with several germanium compositions. The dependence of etch rates on germanium content, etching temperature, and doping concentration are reported. The etch rate and selectivity are approximately exponentially proportional to the germanium content. Etching was found to be insensitive to deposition method, doping method, and annealing conditions of the SiGe films. In addition, etching leaves a smooth silicon substrate surface after removal of SiGe films.     

The diffusion of silicon in germanium

The diffusion coefficients of silicon in germanium as a function of temperature have been measured for the first time. The measurements were performed for lightly doped n-type and p-type germanium; because of the very slight difference observed in diffusion between these cases, the values 2.9 eV for the activation energy and 0.24 cm²/s for the frequency factor can be considered to correspond to those of intrinsic germanium. The ³⁰Si tracer element was implanted into the germanium samples and was detected using the (p, γ) resonance broadening method. The annealing temperatures ranged from 650 to 900°C.     

A review of latchup and electrostatic discharge (ESD) in BiCMOS RF silicon germanium technologies: Part I—ESD

Electrostatic discharge (ESD) continues to be a semiconductor quality and reliability area of interest as semiconductor components are reduced to smaller dimensions. The combination of scaling, design integration, circuit performance objectives, new applications, and the evolving system environments, ESD robustness will continue to be a technology concern. With the transition from silicon bipolar junction transistor to modern BiCMOS silicon germanium (SiGe) semiconductor technologies, new semiconductor process and integration issues have evolved which influence both device performance and ESD protection. Additionally, the issues of low cost, low power and radio frequency (RF) GHz performance objectives has lead to both revolutionary as well as derivative technologies; these have opened new doors for discovery, development and research in the area of on-chip ESD protection and design. With the growth of interest of ESD in RF technology, new innovations and inventions are occurring at a rapid pace. In this paper, we will provide an introductory review of silicon germanium technology and ESD.     

光抽运甲基氟远红外激光器

一、引言 用CO_2激光抽运的远红外激光器诞生在1970年,至今已在30多种分子中获得了1000多条远红外激光谱线,波长范围从40微米到2毫米,复盖了整个远红外区。与电激励远红外激光器相比,光抽运的远红外激光器不存在放电起伏、热漂移和分子分解等现象。因此,具有单色性好,噪声低等优点,特别适用于通讯、雷达、等离子体诊断、光频标与光频测量、光谱学、天文学等领域。     

Overview of low temperature hydrophilic Ge to Si direct bonding for heterogeneous integration

Germanium is gaining interest in two important areas of electronics; for high performance metal oxide semiconductor field effect transistors due to the high carrier mobility and for imaging and optical applications due to its superior absorption in the infrared range. Optimally, germanium will be integrated with existing silicon electronics to enhance electrical and optical properties. One method for integration of germanium with silicon is direct wafer bonding of the two materials. In this paper, wafer-level germanium–silicon heterogeneous integration technologies are investigated and described in detail, including structural and electrical features of bonded hetero-structure.     

Rapid thermal annealing of high-melting-point films onlow-melting-point substrates

Rapid thermal annealing which involves fast heating and cooling rates, is used to activate dopants in thin-film structures yet minimize the dopant diffusion that occurs with excessive thermal exposure. Although the proper resulting electrical properties are the main concern, the structural behavior must also be considered. At the elevated annealing temperature, the heterostructure may be susceptible to both relaxation and yielding. However, the relative effect of these deformations is a function of the material properties, ramp-rate, annealing conditions, and wafer geometry, In particular, for a high-melting-point film on a lower-melting-point substrate, the substrate will experience the inelastic effects prior to the film. More specifically, because germanium has a significantly lower melting point than silicon, previously developed processing technology for silicon cannot be applied directly to germanium processing. A numerical model has been developed to account for the thermo-mechanical effects associated with rapid thermal annealing of relaxing materials. Numerical parametric studies have been conducted for rapid thermal annealing of a thin polysilicon film on a (111) germanium substrate in order to determine the optimum processing window. Results reveal that lower annealing temperatures that still fall within the RTA regime will minimize or even eliminate the plastic damage that could occur during thermal processing     

Germanium on sapphire by wafer bonding

This paper describes the creation of a germanium on sapphire platform, via wafer bonding technology, for system-on-a-chip applications. Similar thermal coefficients of expansion between germanium (5.8 × 10^?6 K^?1) and sapphire (5 × 10^?6 K^?1) make the bonding of germanium to sapphire a reality. Germanium directly bonded to sapphire results in microvoid generation during post bond annealing. Inclusion of an interface layer such as silicon dioxide layer by plasma enhanced chemical vapour deposition, prior to bonding, results in a microvoid free bond interface after annealing. Grinding and polishing of the subsequent germanium layer has been achieved leaving a thick germanium on sapphire (GeOS) substrate. Submicron GeOS layers have also been achieved with hydrogen/helium co-implantation and layer transfer. Circular geometry transistors exhibiting a field effect mobility of 890 cm²/V s have been fabricated onto the thick germanium on sapphire layer.     

Approaches to hydrogenation of silicon tetrachloride in polysilicon manufacture

A review of approaches to hydrogenation of silicon tetrachloride is presented. A byproduct of polysilicon manufacture, silicon tetrachloride is thus converted into trichlorosilane, which is then recycled to reduce the production cost of polysilicon. Catalytic hydrogenation is identified as the most commercially promising line of research and development.     

Design,fabrication, and analysis of transparent silicon solar cells for multi‐junction assemblies

Transparent silicon solar cells can lead to an increased efficiency of silicon‐based multi‐junction assemblies by transmitting near and below band gap energy light for conversion in a low band gap solar cell. This analysis shows that the maximum efficiency gain for a low band gap solar cell beneath silicon at a concentration of 50 suns is 5.8%, based on ideal absorption and conversion of the photons. This work analyzes the trade‐offs between increased near band edge absorption in the silicon and silicon solar cell transparency. Application of these results to real cases including a germanium bottom solar cell is analyzed, leading to a range of cases with increased system efficiency. Non‐ideal surfaces and real silicon and germanium solar cell device performance are presented. The range of practical system gains may be as low as 2.2 – 1% absolute when compared with the efficiency of a light‐trapped silicon solar cell for 1‐sun operation, based on this work. Copyright © 2012 John Wiley & Sons, Ltd.     

新型蒸发器在光纤预制棒生产中的应用

介绍了光纤预制棒的生产工艺以及国内SiCl4蒸发输送系统的技术现状。描述了新型SMR蒸发器的结构特点、技术规格和在SiCl4流量控制方面的优良性能。     

Growth of epitaxial Si1-xGex layers at 750° C by VLPCVD

Silicon-germanium epitaxial layers have been grown on (100) silicon at 750° C by very low pressure chemical vapor deposition (VLPCVD). Pure SiH₄ and GeH₄ were used as the processing gases. Commensurate films of Si_1-x withx < 0.13 have been deposited up to a critical thickness about 2-4 times larger than the equilibrium value. Interrupted growth, controlled by gas switching, was employed to improve interfacial abruptness. The films have been characterized as a function of SiH₄ and GeH₄ flow rates and germanium content. Growth rate and germanium incorporation as a function of GeH₄:SiH₄ input ratio and total gas flow rate have been studied. We observed that the growth rate of the Si_1-x Ge _x layer decreases as the germanium content in the film or the GeH₄:SiH₄ ratio increases at 750° C using VLPCVD. We also found that, for a given GeH₄:SiH₄ ratio, the germanium incorporated in the solid is independent of the total gas flow rate.     

Silicon germanium active layer with graded band gap and µc-Si:H buffer layer for high efficiency thin film solar cells

We investigated solar cells with graded band gap hydrogenated amorphous silicon germanium active layer and hydrogenated microcrystalline silicon buffer layer at the interface of intrinsic and n-type doped layer. A significantly improved, 10.4% device efficiency was observed in this type of single junction solar cell. The intrinsic type microcrystalline silicon buffer layer is thought to play dual roles in the device; as a crystalline seed-layer for growth of n-type hydrogenated microcrystalline silicon layer and helping efficient electron collection across the i/n interface. Based on these, an enhancement in cell parameters such as the open-circuit voltage (V_oc), and fill factor (FF) was observed, where the FF and V_oc reaches up to 69% and 0.85 V respectively. Our investigation shows a simple way to improve device performance with narrow-gap silicon germanium active layer in solar cells in comparison to the conventionally constant band gap device structure.     

硅基BIB红外探测器研究进展

以锗基和硅基为主的阻挡杂质带（blocked impurity band,BIB）红外探测器的兴起有力推进了红外天文学的快速发展,其中硅基BIB红外探测器在特定波长的航天航空领域有着不可替代的地位。国外对硅基BIB红外探测器的研究已有40多年,以美国航空航天局（NASA）为主的科研机构已经实现了硅基BIB红外探测器在天文领域的诸多应用,而国内对硅基BIB红外探测器的研究尚处于起步阶段。本文首先阐述了硅基BIB红外探测器的工作原理,然后简单概述了器件结构和制备工艺,并对不同类型的硅基BIB探测器的性能进行了对比分析,之后介绍了其在天文探测中的应用,最后对硅基BIB红外探测器未来的发展进行了展望。