1628 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 19, NO. 20, OCTOBER 15, 2007 Room-Temperature Operation of Buffer-Free GaSb–AlGaSb Quantum-Well Diode Lasers Grown on a GaAs Platform Emitting at 1.65 m M. Mehta, A. Jallipalli, J. Tatebayashi, Member, IEEE, M. N. Kutty, A. Albrecht, G. Balakrishnan, Member, IEEE, L. R. Dawson, and D. L. Huffaker, Senior Member, IEEE Abstract—Buffer-free growth of GaSb on GaAs using interfacial misfit (IMF) layers may significantly improve the performance of antimonide-based emitters operating between 1.6 and 3 m by in- tegrating III–As and III–Sb materials. Using the IMF, we are able to demonstrate a GaSb–AlGaSb quantum-well laser grown on a GaAs substrate and emitting at 1.65 m, the longest known oper- ating wavelength for this type of device. The device operates in the pulsed mode at room temperature and shows 15-mW peak power at 10 C and shows high characteristic temperature ( ) for an Sb-based active region. Further improvements to IMF formation can lead to high-performance lasers operating up to 3 m. Index Terms—GaAs, GaSb, interfacial misfits (IMFs), semicon- ductor lasers. I. INTRODUCTION A NTIMONIDE (Sb)-based semiconductor lasers are an attractive solution for several applications that require emitters operating beyond standard fiber-based communication wavelengths (1.55 m) such as carbon dioxide and phos- phine detection, excitation of biological molecules for medical sensing, free-space optical communication, and military scene projection. In the last several decades, many researchers have reported Sb-based lasers operating at the near-infrared (NIR) ( 2 m) or midwavelength IR (MWIR) range (between 2 and 5 m) [1]–[11]. Furthermore, high-performance lasers exhibiting very low threshold current density, high modal gain, high characteristics temperature ( ), and high output power have been recently demonstrated [7]–[11]. These characteristics of GaSb-based lasers emitting in the NIR range have made their performance comparable to those of conventional InP-based lasers. Commercialization of these Sb-based devices would be enhanced by developing the devices on an established material platform such as GaAs (or InP) substrates. Interfacial misfit (IMF) arrays offer a method to grow Sb-based layers on a GaAs platform without having to use metamorphic buffer layers to relieve the 8% lattice mismatch between GaAs and GaSb. Since IMF-based growth was first re- ported, the technology has led to the demonstration of optically Manuscript received February 23, 2007; revised June 29, 2007. This work was supported in part by the U.S. Department of Commerce under Grant BS123456. The authors are with the Center for High Technology Materials (CHTM), University of New Mexico (UNM), Albuquerque, NM 87106 USA (e-mail: huffaker@chtm.unm.edu). Digital Object Identifier 10.1109/LPT.2007.904928 pumped GaSb–AlGaSb edge emitters and VCSELs grown on Si substrates and an electrically injected GaSb–AlGaSb vertical-cavity light-emitting diode monolithically embedded between GaAs–AlGaAs distributed Bragg reflectors [12]–[14]. Work has also been conducted on the atomic modeling and the material characterization of the IMF interface [15]. In this letter, we report the demonstration of room-temperature oper- ation of an electrically injected GaSb–AlGaSb quantum-well (QW) laser grown on a GaAs substrate using IMF arrays at the GaAs–GaSb interface. By monolithically integrating a thermally conductive GaAs substrate with an Sb-based active region, we demonstrate, to the best of our knowledge, the longest wavelength QW laser grown on a GaAs substrate. This report presents the foundation for a hybrid As–Sb approach to devices operating between 1.6 and 3 m that might vastly im- prove heat spreading and contact resistance in Sb-based lasers. Improvements in each of these areas will also enable future development of hybrid As-Sb VCSELs, avalanche photodiodes, and photonic integrated circuits. II. DEVICE DESIGN,GROWTH, AND FABRICATION The growth of the laser structure is performed on a V80-H solid-state molecular beam epitaxy reactor. The reactor houses valved Sb and As crackers for precise control of Group V in- corporation during growth. The reactor is also equipped with a RHEED gun, critical to the confirmation of IMF formation during growth. The growth is initiated with a 100-nm GaAs smoothing layer followed by the IMF formation and 5 nm of undoped GaSb growth. After deposition of the undoped GaSb layer, growth proceeds directly to the doped AlGaSb n-type cladding layer. The remainder of the growth is carried out using conventional growth techniques for Sb-based devices. The IMF is formed at the GaAs–GaSb interface through two-dimensional packing of Sb atoms on the GaAs surface. Misfit dislocations that form perpendicular to the plane of growth relieve completely the strain due to the lattice mis- match of the two materials. Moreover, we have confirmed that these misfit dislocations arise in a periodic fashion at a spacing corresponding directly with the lattice mismatch based on high-resolution transmission electron micrograph (TEM) analysis [16]. Previous modeling of the possible strain energies confirms that the formation of an IMF is an energetically favorable scenario during lattice mismatch growth [15]. A schematic of the complete device structure is illustrated in Fig. 1. The p-type and n-type cladding layers are both 1041-1135/$25.00 © 2007 IEEE