IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 9, NO. 2, FEBRUARY 1997 173 InAsSbP–InAsSb–InAs Diode Lasers Emitting at 3.2 m Grown by Metal-Organic Chemical Vapor Deposition D. Wu, E. Kaas, J. Diaz, B. Lane, A. Rybaltowski, H. J. Yi, and M. Razeghi, Senior Member, IEEE Abstract— InAsSb–InAsSbP double heterostructure diode lasers have been grown by metal-organic chemical vapor deposition on (100) InAs substrates. High-output powers of 660 mW in pulse mode and 300 mW in continuous wave operation with 400- m cavity length and 100- m-wide aperture at 78 K have been obtained. These devices showed low threshold current density of 40 A/cm , low internal loss of 3.0 cm , far-field of 34 with differential efficiency of 90% at 78 K, and high operating temperatures of 220 K. Index Terms— High power, InAs, midwave-infrared lasers, MOCVD. C ONSIDERABLE efforts has been devoted to the development of mid-wave infrared (MWIR) lasers with high operating temperatures within the spectral range 3–5 m. The main applications of these MWIR lasers include the free-space communication through the atmospheric transmission windows, the monitoring of the atmospheric gases, and the chemical spectroscopy. At present, several semiconductor material systems such as InAsSb–InAlAsSb [1], InGaAs–InAsSb, InAsSb–InPSb [2], GaInAsSb–AlGaSb [3], or InAsSb(P)–InAsSbP [4] grown by either liquid phase epitaxy or molecular beam epitaxy are being exploited to produce MWIR lasers. In this paper, we report high-power operation of 660 mW in pulse operation, and 300 mW in continuous-wave (CW) operation from a 100- m-wide aperture for InAsSb–InAsSbP–InAs lasers grown by metal- organic chemical vapor deposition (MOCVD). Dependencies of the threshold current density and differential efficiency on cavity length are discussed. Double heterostructures (DH) InAsSb–InAsSbP–InAs were grown on (100) oriented Te-doped InAs substrates by MOCVD under growth conditions similar to those described previously [5]. The DH lasers used in this work consist of an undoped 1.0- m-thick active layer InAs Sb sandwiched between 1.2- m-thick Sn-doped 7 10 cm and Zn-doped 5 10 cm InAs Sb P confining layers with a final layer of p-doped InAs cap layer. To appraise the laser performance, broad-area lasers with 100- m-wide con- tact stripes were fabricated on a p-doped 5 10 cm Manuscript received July 26, 1996; revised October 7, 1996. This work was supported by DARPA/US Army contract DAAH04-95-1-043. The authors are with the Center for Quantum Devices, Department of Elec- trical Engineering and Computer Science, Northwestern University, Evanston, IL 60208 USA. Publisher Item Identifier S 1041-1135(97)01227-5. InAs layer by depositing metal layers of TiPt–Au. A fi- nal n-type ohmic contact is formed on the n-InAs substrate by depositing AuGe–Ni–Au. The 100- m-wide photoresist stripes were defined by classical lift-off process. The InAs cap layer between the patterned stripes is chemically etched using H SO :H SO:H in order to localize the injection current in the lateral direction. Thermal treatment of the p- and n-ohmic contacts is performed at temperatures between 300 C–320 C to obtain low-resistance of 0.2 for diodes at cavity length of 700 m at 78 K. After cleaving, individual diodes are mounted p-side up onto copper heat sinks by indium bonding. Laser diodes with cavity length varying from 300 m to 1800 m were prepared without mirror coating and light char- acteristics were recorded in pulse operation (pulse widths 6 s, repetition rate 200 Hz) using an InSb infrared photodetector. The measurements of light power are based on a calibrated InSb detector. Its responsivity, % peak response for a given wavelength, and trans-impedance gain of a pre-amplifier are given by the manufacturer (EG&G Judson), and yield a correspondence between impingent light power and output voltage. This voltage is measured with a calibrated boxcar averager, additionally controlled with an oscilloscope. To avoid saturation of the detector, we use neutral density filters; linearity of the response to light power is also assured by a matched pre-amplifier, which saturates when the input exceeds a linear regime level. The filters were carefully positioned to avoid interference effects, and then their total attenuation was measured. Losses in light power due to reflections at optical (sapphire) components’ surfaces were taken into account using transmittances of windows given by particular manufacturers. Finally, we multiply such light power by two assuming equal emission from two facets. The light-current characteristics of these DH lasers are illustrated in Figs. 1 and 2. Fig. 1 shows pulsed operation resulting in an output power as high as 660 mW per two facets, emitting at 3.19 m, for a 100- m-wide laser with cavity length of 700 m at 78 K. The differential quantum efficiency corresponding to this cavity length was determined to be 83%, showing no sign of any nonlinearities or kinks. The maximum power in most of the devices was limited by our automated current driver. The inset of Fig. 1 shows the lasing spectrum of the same diode at an output power of 1 mW operating at high temperatures of 220 K 9.5 A). The characteristic temperature for these lasers were in the range of 40–45 K for temperatures up to 130 K. Continuous wave operation at 78 K resulted 1041–1135/97$10.00  1997 IEEE