Optimization of fabrication processes of the mesa-type GaAs:Te blocked-impurity-band detector
In this work, the device structure of the mesa-type GaAs:Te blocked-impurity-band detector was designed. The fabrication processes were presented briefly, and optimization of the fabrication processes was investigated. A 3-micron-thick SiO2 film was deposited as resist to substitute for photoresist in the 50-micron-deep mesa etching process. In addition, a bi-layer photoresist lithography technique was adopted to optimize the process of electrode fabrication. It is demonstrated that the device quality can be improved significantly after optimization.
GaAs BIB photodetector development for far-infrared astronomy
GaAs photoconductive detectors offer an extended spectral response in the far-infrared (FIR) compared to presently available stressed Ge photoconductors. Furthermore, responsivity at wavelengths up to 330 microns can be reached without having to apply uniaxial stress close to the breaking limit on each pixel. This would greatly simplify the production of detector arrays and therefore allow much larger numbers of pixels. Such arrays are highly demanded for upcoming far-infrared astronomy missions with space and airborne telescopes. However, bulk GaAs photoconductors have only limited sensitivity, due to low absorption and high dark currents. Considerable improvement of the detector performance can be expected from the development of GaAs blocked impurity band (BIB) devices. Our recent crystal growth experiments show that the liquid phase epitaxial (LPE) technique is capable of producing the required purity for the blocking layer. We have also performed far-infrared absorption measurements of doped GaAs layers which demonstrate the spectral range extension to about 330 microns and the enlarged absorption coefficient for the more highly doped absorption layer. Experimental work is supported by numerical modeling of BIB devices done in our group.
International EMS systems: New South Wales, Australia.
Australia has an area of 7,692,024 km 2 and a population of 19,169,083. The state of New South Wales (NSW) has an area of 801,428 square kilometres and a population of 6,663,700 (June 2002). It contributes 10% of the land area of Australia and 34% of the population. The length of the coastline is 2007 km with an east-west distance of 1450 km (Fig. 1). Approximately 90% of the NSW population resides within 100 km of the coast. The population density is greatest in the Greater Metropolitan Region around Sydney, an area of 1580 square km, population of 4,154,722. Only 0.6% live in regions classified as remote or very remote (based upon distance to regional townships). The climate is generally mild, although temperature extremes range from � /20 8C (Charlotte’s Pass) to 50 8C (far Western NSW). The highest point is 2228 m at Mt. Kosciuszko. However, most of NSW is below 500 m in altitude.