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Device Degradation (device + degradation)

Distribution by Scientific Domains

Engineering	40%

Selected Abstracts

Hydrogen- and carbon-related defects in heavily carbon-doped GaAs induced degradation under minority-carrier injection

ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 5 2010
Hiroshi Fushimi
Abstract GaAs/AlGaAs heterojunction bipolar transistors (HBTs) have attracted much attention because of their high-speed performance. However, long-term operation seriously degrades the device characteristics: the current gain decreases and the low-bias-leakage current increases. This degradation has long been an issue in GaAs-based devices operated under minority-carrier injection, such as laser diodes. The cause of degradation is thought to lie in the carbon-doped base, but this is not yet certain. In this paper the degradation of HBTs is described, especially that of GaAs/AlGaAs HBTs with a heavily carbon-doped base layer. Two types of device degradation are found, namely, hydrogen-related degradation and carbon-related degradation. The mechanisms governing the degradation are discussed in the framework of the recombination-enhanced defect reaction (REDR) and charge state effect (CSE). © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(5): 33,41, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10208 [source]

Enhanced Thermal Stability and Efficiency of Polymer Bulk-Heterojunction Solar Cells by Low-Temperature Drying of the Active Layer

ADVANCED FUNCTIONAL MATERIALS, Issue 5 2010
Ching Lin
Abstract This study addresses two key issues, stability and efficiency, of polymer solar cells based on blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) by demonstrating a film-forming process that involves low-temperature drying (,5,°C) and subsequent annealing of the active layer. The low-temperature process achieves 4.70% power conversion efficiency (PCE) and ,1250,h storage half-life at 65,°C, which are significant improvements over the 3.39% PCE and ,143,h half-life of the regular room-temperature process. The improvements are attributed to the enhanced nucleation of P3HT crystallites as well as the minimized separation of the P3HT and PCBM phases at the low drying temperature, which upon post-drying annealing results in a morphology consisting of small PCBM-rich domains interspersed within a densely interconnected P3HT crystal network. This morphology provides ample bulk-heterojunction area for charge generation while allowing for facile charge transport; moreover, the P3HT crystal network serves as an immobile frame at heating temperatures less than the melting point (Tm) of P3HT, thus preventing PCBM/P3HT phase separation and the corresponding device degradation. [source]

A Delivery System for Self-Healing Inorganic Films,

ADVANCED FUNCTIONAL MATERIALS, Issue 22 2008
Harvey A. Liu
Abstract Multilayer composites that utilize polymeric and brittle inorganic films are essential components for extending the lifetimes and exploiting the flexibility of many electronic devices. However, crack formation within the brittle inorganic layers that arise from defects as well as the flexing of these multilayer composite materials allows the influx of atmospheric water, a major source of device degradation. Thus, a composite material that can initiate self-healing upon the influx of environmental water through defects or stress-induced cracks would find potential applications in multilayer composite materials for permeation barriers. In the present study, the reactive metal oxide precursor TiCl4 is encapsulated within the pores of a degradable polymer, poly(lactic acid) (PLA). Electrospun PLA fibers are found to be reactive to atmospheric water leading to the hydrolysis of the degradable polymer shell and subsequent release of the reactive metal oxide precursor. Release of the reactive TiCl4 from the pores results in hydrolysis of the metal oxide precursor, forming solid titanium oxides at the surface of the fibers. The efficacy of this self-healing delivery system is also demonstrated by the integration of these reactive fibers in the polymer planarization layer, poly(methyl methacrylate), of a multilayer film, upon which an alumina barrier layer is deposited. The introduction of nanocracks in the alumina barrier layer lead to the release of the metal oxide precursor from the pores of the fibers and the formation of titanium dioxide nanoparticles within the crack and upon the thin film surface. In this study the first delivery system that may find utility for the self-healing of multilayer barrier films through the site-specific delivery of metal oxide nanoparticles through smart reactive composite fibers is established. [source]

Impact of probe-to-pad contact degradation on the high frequency characteristics of RF MOSFETs and guidelines to avoid it

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 3 2001
E. P. Vandamme
Abstract Apparent degradation of the RF characteristics of silicon MOSFETs was observed under normal operating conditions. We show that it was not caused by intrinsic device degradation but originated from a degradation of the contact resistance between probe and bonding pad. Guidelines, not limited to MOSFETs only, are given that enable accurate S -parameter measurements for RF modelling and reliability assessment. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 114,120, 2001. [source]

Inside Back Cover (Phys. Status Solidi A 5/2010)

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2010
J. H. Leach
The Feature Article by Morkoç and co-workers (pp. 1091,1100) centers around the not so intuitive phenomena in two types of GaN based devices, namely InGaN based LEDs and InAlN barrier GaN heterojunction FETs. In terms of the LEDs, the paper uncovers that the quantum efficiency degradation observed at high current injection levels is not necessarily of Auger recombination origin. Furthermore, nearly similar behavior of LEDs on c-plane and mplane suggests that the main driving force for the efficiency degradation is not polarization induced field either. The data along with their interpretation should set the stage for an accurate physics- based model to be developed. In terms of the FETs, the authors show that there is an optimum sheet density, which depends on drain bias or the electric field in the channel, at which the LO phonon lifetime is shortest, the velocity is highest, and the device degradation is least. The average optimum density is near 7 × 1012 cm,2 which challenges the proverbial notion that the higher the sheet density the better it is. Another outcome of this discussion is that heat dissipation takes the route of hot electrons giving off heat to LO phonons which in turn give it to LA phonons when they decay. Naturally, the shortest LO phonon lifetime is best for heat removal and thus the devices are more reliable in addition to electrons traversing at the highest velocity. [source]