High pulse power, mid-infrared AlGaAs/GaAs-quantum cascade lasers (QCLs) operation with no cryogenic cooling is reported. The laser design followed 3QW anticrossed-diagonal scheme [1]. The structures used double-plasmon Al-free waveguide for planar optical confinement. The injector doping was ~ 2.2x10¹²cm^-2 per period.

The electronic band structure of QCL has been calculated by solving Schroedinger equation with position dependent effective mass by finite difference method. The laser structures were grown by solid source MBE. The (100) oriented GaAs n+ substrates were used. The substrate temperature T_s was kept at 580 ⁰C. The value of V/III ratio was at least 35 for growth of both GaAs and Al_0.45Ga_0.55As layers [3][4].

For obtaining information about thickness and a composition of component layers of both test structures and a complete QCL structures, the analysis of double-crystal rocking curves was carried out. The dynamical diffraction theory has been used for simulating the symmetric (004) reflections, leading to extraction of structural parameters of periodic structures. The better than 1% thickness accuracy has been routinely achieved for lasing structures.

The double trench lasers were fabricated using standard processing technology, i.e., wet etching and Si₃N₄ for electrical insulation. The low resistivity Ni/AuGe/Ni/Au ohmic contacts, alloyed in 430⁰C, were used at the top of the devices. After the wafer was thinned down to about 100 mm, an alloyed AuGe/Ni/Au contact was deposited on the backside. For current injection, windows were opened through the insulator with width 25, 35, and 50 mm. The lasers were cleaved into bars of  1 and 2.5 mm length and soldered with Au/Sn eutectic, epilayer down on diamond heatspreader and copper submounts. The devices emitted at 9.4 mm and operated up to 240 K, in pulsed mode with powers ~ 1W (77 K) and few mW (240 K) with slope efficiency h»0.70 W/A per uncoated facet.

[1]    H. Page, C. Becker, A. Robertson, G. Glastre, V. Ortiz, C. Sirtori, Applied Physics Letters, vol.78,. 3529 (2001).

[2]   K. Kosiel, J. Kubacka-Traczyk, P. Karbownik, A. Szerling, J. Muszalski, M. Bugajski, P. Romanowski, J.Gaca, M. Wójcik, Microelectronics Journal, vol. 40, 565 (2009)

[3]   K. Kosiel, M. Bugajski, A. Szerling, J. Kubacka-Traczyk, P. Karbownik, E. Pruszyńska-Karbownik,

        J. Muszalski, A. Łaszcz, P. Romanowski, M. Wasiak, W. Nakwaski, I. Makarowa, P. Perlin, Photonics

        Letters Poland, vol..1, 16 (2009)

[4]   K. Kosiel, M. Bugajski, A. Szerling, J. Kubacka-Traczyk, P. Karbownik, J. Muszalski, P. Romanowski,

        15th European Molecular beam Epitaxy Workshop, March 8-11, 2009, Zakopane, Poland

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