InP/InGaAlAs distributed Bragg reflectors grown by low-pressure metal organic chemical vapor deposition

Abstract

Long-wavelength vertical cavity surface emitting lasers (VCSELs) are considered the best candidate for the future low-cost reliable light sources in fiber communications. However, the absence of high refractive index contrast in InP-lattice-matched materials impeded the development of 1.3-1.5 mum VCSELs. Although wafer fusions provided the alternative approaches to integrate the InP-based gain materials with the GaAs/AlAs materials for their inherent high refractive index contrast, the monolithic InP-based lattice-matched distributed Bragg reflectors (DBRs) are still highly attractive and desirable. In this report, we demonstrate InP/InGaAlAs DBRs with. larger refractive index contrast than InP/InGaAsP and InAlAs/InGaAlAs DBRs. The switching between InP and InGaAlAs layers and growth rate control have been done by careful growth interruption technique and accurate in situ optical monitoring in low-pressure metal organic chemical vapor deposition. A 35 pairs 1.55 mum centered InP/InGaAlAs DBRs has the stopband of more than 100 nut and the highest reflectivity of more than 99%. A VCSEL structure incorporating 3 5 pairs InP/InGaAlAs DBR as the bottom mirror combined with a 2lambda thick periodic gain cavity and 10 pairs SiO2/TiO2 top dielectric mirrors was fabricated. The VCSELs lased at 1.56 mum by optical pumping at room temperature with the threshold pumping power of 30 mW. (C) 2002 Elsevier Science B.V. All rights reserved.