Characterization of GaAs/(GaAs)n(AlAs)m surface-emitting laser structures through reflectivity and high-resolution electron microscopy measurements

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Abstract
Careful investigation of the reflectivity of two very high finesse integrated Fabry–Perot interferometers is reported. These two structures, made of GaAs active layer (1.7 μm thick) surrounded by two superlattice/AlAs Bragg reflectors, exhibit vertical cw lasing action at and above room temperature when photopumped with thresholds of 16 mW at 300 K and 56 mW at 380 K. Reflectivity measurements together with theoretical calculations show that layer regularity, accurate thickness control, and low interface roughness are key parameters for high-performance structures. Transmission electron microscopy on cleaved wedges and reflection electron microscopy are shown to be unique tools for measuring and characterizing these layers. Electron microscopy, optical reflection, and laser linewidth measurements are correlated and show that the layer flatness is dramatically increased by the introduction of six (2.5 Å) GaAs wells in the AlAs growth of the integrated dielectric reflectors. Reflectives of 97%, Fabry–Perot finesse as high as 100 (61 for direct measurements), and laser linewidths as small as 1.2 Å are reported.