MOLECULAR-BEAM EPITAXY GROWTH AND CHARACTERIZATIONS OF ALGAASSB ALASSB BRAGG REFLECTORS ON INP/

The molecular beam epitaxy growth of AlAsSb/Al0.04Ga0.96AsSb distribut ed Bragg reflectors lattice-matched to InP is studied. The fabrication and characterization of two such reflectors are reported. Fine struct ural and optical properties of these samples are investigated using do uble crystal X-ray diffraction, scanning electron microscopy and refle ctivity measurements. Main device performances are a 260 nm wide stop- band centred at 1.55 mu m with a maximum reflectivity of 90% for the f irst 8.5 pairs Bragg reflector while the second 15.5 pairs reflector h ave allowed an improved maximum reflectivity exceeding 96% at 1.6 mu m with a stop-band of 220 nm. As a major result, a new type of surface defects is observed on the AlGaAsSb/AlAsSb Bragg reflector surface. Pl anar and cross-sectional microscopic observation has revealed that def ects are initiated from the reflector-substrate interface. The formati on of these defects are discussed and it has been related to InAs isla nds that appear during the in situ InP-substrate oxide desorption proc edure.