Small footprint InGaSb/AlGaAsSb multiple-quantum-well light-emitting diodes

Abstract

ABSTRACT 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. Yakovlev’s 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