Vertical-cavity surface-emitting lasers are attractive light sources particularly for gas-sensing applications. Using the AlGalnAs/lnP material system, an emission wavelength ranges from 1.3 to 2.05 mu m has already been achieved [G. Boehm, M. Ortsiefer R. Shau, J. Rosskopf, C. Lauer, M. Manic, F. Kohler, F. Mederer, R. Meyer, M.-C. Amann, in: Proceedings of MBE XII, J. Crystal Growth (2002) pp. 748-753]. Within this range, absorption lines of gases like H2S (1590 nm), CH4 (1654 nm), H2O (1877 nm) and CO2 (2004 nm) are detectable [G. Totschnig, M. Lackner, R. Shan, M. Ortsiefer, J. Rosskopf, M.-C. Amann, F. Winter, Meas. Sci. Technol. 14 (2003) 472]. The aim of this work is a further expansion of the emission wavelength up to 2.3 mu m, exploiting the well-known InP-based material system and the fabrication technique of buried tunnel junction (BTJ) VCSELs [R. Shau, M. Ortsiefer, J. Rosskopf, G. Boehm, C. Lauer, M. Maute, M.-C. Amann, in: Proceedings of SPIE, 5364 (2004) 1-15) to reach the technologically important absorption lines of carbon monoxide (CO) around 2.33 mu m. (c) 2006 Elsevier B.V. All rights reserved.