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In 1991, Soref and Perry presented a concept paper on the properties of a hypothetical ternary Ge1−x−ySixSny alloy for silicon-compatible optoelectronic applications.1 The material was finally synthesized at Arizona State University in 2003,2 opening up a new field of research that is rapidly approaching its first one-thousand publications. A very recent review article by Wirths, Buca, and Mantl provides...
Light emission from Si, would allow integration of electronic and optical functionality in the main electronics platform technology, but this has been impossible due to the indirect band gap of Si. In this talk I will discuss 2 different approaches, using unique properties of nanowires, to realize light emission from Si-based compounds.
Flexible electronics using gallium arsenide (GaAs) for nano-electronics with high electron mobility and optoelectronics with direct band gap are attractive for many applications. Here we describe a state-of-the-art CMOS compatible batch fabrication process of transforming traditional electronic circuitry into large-area flexible, semi-transparent platform. We show a simple release process for peeling...
Ge is an indirect bandgap material for research interest with possible photonic applications. In previous work, only direct bandgap emission was observed in the epitaxial Ge on Si, but both direct and indirect emissions were observed in the bulk Ge substrates. This discrepancy between epitaxial Ge and Ge substrate may be due to reabsorption of direct emission. In this work, the reabsorption is systematically...
In recent years the class of dilute nitride III/V-semiconductors and corresponding heterostructures are gaining increasing interest both from fundamental as well as applied point of view. This is caused by their unique optoelectronic properties and in particular by the novel conduction band formation process leading to an extreme band gap bowing with increasing N-content in the crystal.
The performance and material quality requirements of thin film a-Si/c-Si1−xGex/Si heterojunction solar cells are investigated by modeling and simulation. The effects of Ge content, Si1−xGex thickness, Si1−xGex lifetime and a-Si/c-Si1−xGex interfacial quality have been studied. The simulations predict that Si1−xGex based thin film solar cells provide a significant increase in solar cell output current...
Efficiency limits of single-junction and multi-junction concentrator solar cells are established from the thermodynamic principle of detailed balance. The maximum efficiency limit of single-junction solar cells is 35% at 500 suns, while that of 2-junction solar cells which meet the current matching condition is 46%. At the same condition, the maximum efficiency limit of 3-junction solar cells with...
The work presented here aims to reduce the cost of multijunction solar cell technology by developing ways to manufacture them on cheap substrates such as silicon. In particular, our main objective is the growth of III-V semiconductors on silicon substrates for photovoltaic applications. The goal is to create a GaAsP/Si virtual substrates onto which other III-V cells could be integrated with an interesting...
The novel direct band gap, dilute nitride Ga(NAsP)-material system allows for the first time the monolithic integration of a III/V laser material lattice matched to Si substrate. This lattice-matched approach offers the possibility for a high-quality, low defect density integration of a III/V-laser material potentially leading to long-term stable laser devices on Si-substrate. The present paper introduces...
Recently, Ge has been intensively studied as a light emission material that emits at ~1.5 μm, as it has been theoretically proven to be a promising candidate to realize Si-based light source for on-chip and chip-to-chip communications. In this paper, photoluminescence (PL) is reported from heavily phosphorus (P)-implanted epitaxial Ge thin films on Si. Sheet resistance has been measured to characterize...
Heteroepitaxy SiGe on Si by liquid phase epitaxy (LPE) is a potential material for photovoltaic application. The Si0.05Ge0.95 solar cell with an energy gap of 0.72 eV can lead to a 7 percentage point increase in the Si-based multi-bandgap system or any multi-bandgap system that contains Si as the 1.1 eV solar cell. In this initial work we report first growth SixGe1-x with 0.5<x<1 on Si substrate...
The semiconductor-dielectric interface passivation of Ge pMOSFETs with an epitaxially grown Si-layer is studied by means of the full conductance technique. This technique resolves several issues which occur for alternative MOS-interfaces when using the dasiaclassicalpsila conductance technique. The observed mobility behavior as a function of Si-passivation thickness can be explained by the observed...
We demonstrate that the cryogenic (e.g., 77K=LNT) properties of SiGe-base heterojunction bipolar transistors and circuits are sufficiently advanced to warrant a serious consideration of the merits of cryogenic BiCMOS technologies for future LNT computer applications. In this paper we review the features of epitaxial SiGe-base bipolar technologies which make them particularly Suitable for LNT operation,...
Bandgap narrowing in p-type epitaxial silicon uniformly doped with boron in the concentration range 2??1017 to 5??1018cm??3 is evaluated from the temperature dependence of the collector current of npn bipolar transistors. The study is focussed on the sensitivity of the extracted bandgap narrowing to the model used to describe the intrinsic carrier concentration in pure silicon.
We have synthesized Si1-y Cyand Si1-x-yCyGexalloys using Molecular Beam Epitaxy. When combined with the Si-Ge system. the new ternary system offers greater versatility and freedom in strain and bandgap engineering. Unlike the Si-Ge system the Si-C system has a high misfit (52%) and low solubility (≪ 10-6), with a propensity to compound formation, therefore. the structures are kinetically stabilized...
Different types of bipolar transistor emitters are described. Epitaxial emitters can be achieved by solid phase epitaxial regrowth of polysilicon (at T ≫ 850??C) and recently by glow discharge deposition at T = 250??C and recrystallization (at T = 700??C). Wide band gap emitters and narrow bandgap bases result in very high emitter efficiency which has to be traded-off with emitter and base series...
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