|About this Abstract
||2010 Electronic Materials Conference
||TMS 2010 Electronic Materials Conference
||X9, Antimonide VECSELs on AlGaAs DBRs
||P. Ahirwar, T. J. Rotter, A. R. Albrecht, S. Clark, C.P. Hains, L. R. Dawson, G. Balakrishnan, J. V. Moloney
|On-Site Speaker (Planned)
||T. J. Rotter
We present an optically pumped vertical-external-cavity surface-emitting laser (VECSEL) with high output power at 2 Ám achieved through the integration of III-Sb active regions with AlGaAs Distributed Bragg Reflectors (DBRs)<sup></sup>. The laser’s active region includes GaInSb/AlGaSb type I quantum wells. The optical cavity is provided by a high reflectivity AlGaAs/GaAs DBR and an external mirror which also serves as the output coupler. The novelty in this approach is the combination of a GaSb based active region with a GaAs based DBR, both of which are monolithically grown on a GaAs substrate<sup></sup>. The strain due to the lattice mismatch between the GaSb-based active region (lattice constant close to 6.1 ┼) and the GaAs-based DBR (lattice constant close to 5.65 ┼) is relieved by the formation of an interfacial misfit (IMF) array at the GaSb/GaAs interface<sup>[3,4]</sup>. GaSb based VECSELs were previously grown on GaSb based DBRs. While high power devices have been achieved with this technology, the device performance is limited by a smaller index contrast of GaSb based DBRs compared to GaAs based DBRs and higher absorption of the laser’s emission in GaSb compared to GaAs. The work described in this talk is based on crystal growth by molecular beam epitaxy (MBE), along with the basic crystal characterization techniques such as X-ray diffraction (XRD), photoluminescence (PL), surface nomarski microscopy and atomic force microscopy (AFM). We shall also provide detailed lasing data for lasers at 2 Ám both pulsed and CW. We shall discuss the technical challenges related to the MBE growth of such structures, which are numerous. First, the IMF based growth of III-Sb on GaAs leads to differences in strain and relaxation of the epilayer as compared to growth on GaSb substrates. This influences the optical emission from the III-Sb active region, since it depends on the compressive strain in the quantum wells. It requires an independent development of the active region, grown on GaAs. Second, the transfer of the IMF growth technology from growth on GaAs substrates to growth on the MOCVD grown AlGaAs/GaAs DBR is nontrivial. The challenges include the IMF formation on the DBR surface, which is slightly rougher than a GaAs substrate’s surface, and the growth temperature control, since the DBR’s heat conductivity differs from that of a GaAs substrate. We shall also discuss the development of longer wavelength VECSELs in the MWIR (2.5 to 3.5 Ám). This discussion will include active region development and DBR performance at these wavelengths.