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Mid-infrared light-emitting diodes with InGaSb/AlGaAsSb triple-quantum-well active region have been integrated into arrays of either 200u 200 µm 2 or 40u 40 µm square pixels. Two generations of arrays have been designed, fabricated and tested. The first, sparse 6u 6 array provided valuable information on optimal electrode design and fabrication parameters that was used in the design and processing of the second generation dense 11 u 11 array. Keywords: Light-emitting diodes; Mid-infrared emitters; Optoelectronic integration 1. INTRODUCTION Compared to the intense research on semi conductor lasers emitting in the mid-infrared (mid-IR) range, the interest in mid-IR light-emitting diodes (LEDs) seems to be significantly smaller. The main potential applications of single-emitter mid-IR LEDs are in environmental monito ring, chemical process control, and me dical diagnostics. There are two main groups that have repeatedly published their results on mid-IR LEDs over the past five years. The first group, led by Tony Krier at Lancaster University in the United Kingdom, has fabricated and tested LEDs emitting at wavelengths of 3.3 3.6 µm. These bulk junction devices were grown using liquid phase epitaxy (LPE) on InAs substrates [Krier 2001], [Krier 2003], [Monakhov 2004], [Krier 2006]. Y. P. Yakovlev leads the second group, based at the A. F. Ioffe Physico-Technical Institute in Russia, with focus on bulk p-n junction LEDs grown on GaSb substrates. Yakovlevs group used metal organic chemical vapor deposition (MOCVD) as well as LPE to grow a variety of device structures with emission wavelengths covering the spectral range of 1.6 4.4 µm [Kizhayev 2002], [Stoyanov 2003], [Zhurtanov 2005], [Danilova 2005]. A systematic research effort towards development of two-di mensional arrays of mid-IR emitters has been going on at the US Army Research Laboratory (ARL) in Adelphi, MD [Das 2004], [Das 20 05a], [Das 2005b], [Das 2005c], [Das 2006]. In contrast to the bipolar p-n junction devices reported in this paper, the ARL group uses a unipolar quantum cascade design to generate light. For mounting, a flip-chip t echnique was used, where individual pixel elements varying in size from 200u 200 µm |
