Defect study of GaInP/GaAs based heterojunction bipolar transistor emitter layer

Defects in the emitter region of Ga0.51In0.49P/GaAs heterojunction bipolar transistors (HBTs) were investigated by means of deep-level transient spectroscopy. Both annealed (635 degreesC, 5 min) and as grown metalorganic chemical vapor deposition epitaxial wafers were investigated in this study, with an electron trap observed in the HBT emitter space-charge region from both wafers. The deep-level activation energy was determined to be 0.87+/-0.05 eV below the conduction band, the capture cross section 3x10(-14) cm(2) and the defect density of the order of 10(14) cm(-3). This defect was also found to be localized at the emitter-base interface

Decentralization and regional government size in Spain

The aim of this paper is to investigate the impact of fiscal decen- tralization on the size of regional governments in Spain, by controlling for economies of scale, interregional heterogeneity and institutional framework. We study it over 1985 to 2004 using a panel dataset of seventeen spanish regions. The results can be easily summarized. Firstly, it supports the classic public goods theory of a trade-off-between the economic benefits of size and the costs of heterogeneity. Secondly, it doesn’t reject the “Leviathan” hypoth- esis and neither does the “common pool” hypothesis. Thirdly, by contrast, the paper partly rejects the “Wallis”’ hypothesis. It argues that government size is mediated by financial resources obtained through intergovernmental grants, consistent with welfare economics and positive economic policies. We conclude that later advances in the decentralisation process must be compatible with the goal of reducing fiscal imbalances that emanate from the vertical structure of fiscal power.info:eu-repo/semantics/publishedVersio

New determination of the 3He mixing ratio in the Earth's lower atmosphere from an international tritium intercomparison exercise

International audienceThe light isotope of helium, 3He, is essentially a primordial substance entrapped within the Earth's interior during the formation of the planet. It is released into the atmosphere by volcanic/magmatic activity, and eventually escapes to outer space. 3He is also produced by the radioactive beta-decay of tritium. Hence, measurements of 3He can be used to derive the concentration of tritium. The so-called “3He ingrowth” method uses a mass spectrometer to detect the amount of 3He that accumulates in a sample during a given period of storage. The 3He measurements are classically calibrated against an air standard. The method thus relies on the accurate knowledge of the atmospheric mixing ratio of 3He. This value is based on mass spectrometric measurements with gravimetrically or volumetrically prepared 3He standard mixtures. Here, we apply the 3He ingrowth method in reverse, using a solution of tritiated water prepared for an international comparison of tritium activity measurements to precisely determine the 3He mixing ratio of our air standard. The measured atmospheric mixing ratio of 3He, based on a series of ten measurements, is [3He] = 7.12 ± 0.06 ppt. This value is between 1% and 2% lower than previous determinations reported in the literature. However, all results remain statistically consistent

Measurement of the French national tritiated-water standard by helium-3 mass spectrometry

International audienceThe (3)He ingrowth technique is based on the detection of the tritium radioactive daughter, (3)He, by mass spectrometry. Over the last three decades it has been used extensively in oceanography and groundwater studies for measurements of very low to ultra-low levels of tritium. To compare it with the best available methods of radioactive counting, we applied this method to measure the massic activity of a tritiated-water primary standard prepared by the French Laboratoire National Henri Becquerel (LNHB). One liter of a low-level tritium solution was prepared from a small aliquot of the LNHB standard by two-step gravimetric dilution with tritium-free groundwater. Sixteen samples of this solution were analyzed at the LSCE-Saclay noble gas facility, using the (3)He ingrowth method. The massic activity of the prepared solution was also measured by Liquid Scintillation Counting using the Quantulus LNHB counter and an internal calibration method with the LNHB tritiated water standard. All results agree within their standard uncertainty

International Comparison of Measurements of the Specific Activity of Tritiated Water.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

The correlation between material properties and HBT reliability

The impact of the material quality on the reliability of heterojunction bipolar transistors (HBT) is discussed. So far, a clear impact of the material structure is clearly found on the electrical performances of HBT's. The InGaP/GaAs heterostructure shows impressive reliability figure compared to the AlGaAs/GaAs ones. This behavior is strongly related to the surface passivation of the extrinsic base layer. Three main behaviors are believed to have a positive impact on the reliability: higher electron injection, better stability of the InGaP material, better InGaP passivation. Aging tests have been carried out for more than 6,500hr on 100 devices without any catastrophic failure at stress as high as junction temperature of 200°C and collector current of 40kA cm-2. This result confirms the excellent reliability of InGaP/GaAs HBT and enables to use them in high power applications