IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 21, NO. 15, AUGUST 1, 2009 1087 GaSb-Based Type I Quantum-Well Light-Emitting Diode Addressable Array Operated at Wavelengths Up to 3.66 m Seungyong Jung, Sergey Suchalkin, Gela Kipshidze, Member, IEEE, David Westerfeld, Member, IEEE, Donald Snyder, Matthew Johnson, and Gregory Belenky, Fellow, IEEE Abstract—Type I GaSb-based light-emitting diodes (LEDs) have been demonstrated while operating at room temperature at wavelengths up to 3.66 m with approximately 200 W of quasi-continuous-wave optical power. A mid-infrared 6 6 addressable array of Type I LEDs was also demonstrated. Index Terms—Infrared (IR) scene projection, mid-infrared (mid-IR) light-emitting diode (LED), type I. H IGH brightness and high efficiency broadband light sources for the spectral range 2–5 m are in high de- mand for industrial chemical sensing, process monitoring and mid-infrared (mid-IR) imaging. A central element of these technologies is an individually addressable emitter array for IR image projection. Several approaches have been used for IR image generation including resistor arrays [1], scanning laser arrays [2], and digital micromirror devices, but light-emitting diode (LED) arrays show promise in this application by offering higher spectral brightness, more compact size, relatively higher efficiency, and the possibility of faster modulation. This basic research into mid-IR LEDs as an emitter array combines the advantages of high brightness, high dynamic range, uniformity, temperature stability, fast modulation (high frame rate), low cost, and high reliability. Type II interband cascade (IC) LEDs operating in the spectral range 3–5 m were successfully used for array fabrication [3], but recent progress in the development of Type I GaSb-based mid-IR emitters operating at wavelengths beyond 3 m will open the way for the application of LED emitter arrays in IR scene projection [4]. The Type I mid-IR GaSb-based LED with a quantum-well active region has demonstrated high output power and internal Manuscript received March 02, 2009; revised April 22, 2009. Current version published July 17, 2009. This work was supported by the United States Air Force under Contract FA8651-07-C-0152 and by ARO grant W911NF0610399. S. Jung, G. Kipshidze, and G. Belenky are with the Electrical and Com- puter Engineering Department, SUNY at Stony Brook, NY 11794 USA (e-mail: seung@ece.sunysb.edu; gela@ece.sunysb.edu; garik@ece.sunysb.edu). S. Suchalkin and D. Westerfeld are with the Power Photonics Corporation, Stony Brook, NY 11794 USA (e-mail: suchal@ece.sunysb.edu; davidwester- feld@yahoo.com). D. Snyder and M. Johnson are with Airforce Research Laboratory, Eglin Air Force Base, FL 32542 USA (e-mail: snyder@eglin.af.mil; matthew.johnson@eglin.af.mil). Digital Object Identifier 10.1109/LPT.2009.2022843 Fig. 1. Schemes and mid-IR images of (a) nonaddressable and (b) addressable LED arrays. efficiency [5]. A combination of quinternary AlGaInAsSb bar- riers and quaternary InGaAsSb quantum wells in the device ac- tive area allowed for improvement in hole confinement and re- duction of the bandgap difference between barrier and quantum- well materials. This approach reduces quantum defect and heat generation in the active area. In this letter, we report fundamental research into GaSb-based Type I mid-IR LEDs and LED arrays operating over mid-IR wavelengths up to 3.66 m. The structures were grown on n-type GaSb substrates using a Veeco GEN950 molecular beam epitaxy system. The active area with four InGaAsSb quantum wells separated by AlInGaAsSb barriers was sandwiched between AlGaAsSb claddings. Two kinds of LED arrays were processed (Fig. 1) to study the effect of current spreading to the array performance. The first was an array with the pixels formed by m rectangular windows in the dielectric which separated the metal contact from the epilayer of the structure [Fig. 1(a)]. No grooves were etched between the pixels. Despite the fact that we used a common metallization for all the array pixels, this design can be easily applied to the addressable arrays by depositing a separate contact for each pixel. The second was an array with the m rectangular mesas formed by etching 200- m-wide grooves [Fig. 1(b)]. The epilayer in the grooves was etched down to the buffer layer. After etching, the structure was covered with 1041-1135/$25.00 © 2009 IEEE Authorized licensed use limited to: SUNY AT STONY BROOK. Downloaded on August 28, 2009 at 11:43 from IEEE Xplore. Restrictions apply.