INGAAS(0.98 MU-M) GAAS VERTICAL-CAVITY SURFACE-EMITTING LASER GROWN BY GAS-SOURCE MOLECULAR-BEAM EPITAXY/

We report the growth of InGaAs/GaAs vertical cavity surface emitting l asers (VCSELs) with an emission wavelength at 0.98 mum by gas-source m olecular beam epitaxy (GSMBE). The surface emitting laser diodes are c omposed of a 15-pair p+ GaAs/AlAs graded mirror with a 3-quantum well In0.2Ga0.8As active region and a 16.5-pair n+ GaAs/AlAs grade mirror o n an n+ GaAs substrate. We use a simple interferometric technique for in-situ monitoring and feedback control of layer thickness to obtain a highly reproducible Bragg reflector. This technique uses an optical p yrometer to measure apparent temperature oscillations of the growing e pi-layer surface. These measurements can be performed with continuous substrate rotation and without any growth interruption. The growing la yer thickness can then be related to the apparent temperature oscillat ion spectrum. When the layer reaches the desired thickness, the growth of the subsequent layer is then initiated. By making layer thickness measurements and control in real-time throughout the entire growth cyc le of the structure, the center of the mirror reflectivity and the Fab ry-Perot resonance at the desired wavelength can be reproducibly obtai ned. The reproducibility of the center wavelength and FWHM of the refl ectivity stop-band with a variation of less-than-or-equal-to 0.2% was achieved in the AlAs/GaAs mirror stacks grown using this technique. Th e VCSEL structures with a variation of the Fabry-Perot wavelength of l ess-than-or-equal-to 0.4% have been grown. Bottom-emitting laser diode s were fabricated and operated CW at room temperature. CW threshold cu rrents of 3 and 6 mA are measured at room temperature for 10 and 25 mu m diameter lasers, respectively. Output powers higher than 15 mW are o btained from these devices. These devices have an external quantum eff iciency higher than 40%.