GaInNAs Material Properties for Long Wavelength Opto-Electronic Devices
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GaInNAs Material Properties for Long Wavelength Opto-Electronic Devices Vincent Gambin, Wonill Ha, Mark Wistey, Seongsin Kim1 , James S. Harris Solid State and Photonics Lab, Stanford University, Stanford, CA 94305, U.S.A. 1 Agilent Technologies Palo Alto, CA 94303 ABSTRACT Dilute nitrogen GaInNAs is a new promising material as an active region for use in 1.3 and 1.55 µm opto-electronic devices. It has been commonly observed that increasing the nitrogen content generally reduces the optical emission intensity and increases laser threshold. However, some non-radiative recombination defects are removed from the material during a post-growth anneal. One drawback to the anneal is that nitrogen out-diffuses from the quantum wells and blue-shifts optical emission. Using a modified active region structure, we have decreased nitrogen out-diffusion and reduced the luminescence blue-shift while still improving crystal quality. The growth consists of high nitrogen GaNAs barriers grown between lower nitrogen GaInNAs quantum wells. As an added benefit, the nitride barriers strain compensate for the compression in the high In content GaInNAs wells. Furthermore, in order to improve luminescence at long wavelengths, we have added Sb to GaInNAs and have observed high intensity photoluminescence (PL) out to 1.6 µm. We have grown and fabricated in-plane GaInNAs lasers that emit at 1.3 µm with a current threshold density of 1.2 kA/cm2 and GaInNAsSb lasers with emissions at 1.46 µm with a current threshold of 2.8 kA/cm2 . INTRODUCTION There currently is a high demand for low cost 1.3-1.55 µm diode lasers that can operate over a significant temperature range (-10 to 85ºC) with moderate power (>10 mW). There are many applications for light sources in this wavelength region including telecommunication lasers, modulators and amplifiers. Current solutions based on InP have serious limitations covering the entire 1.3-1.55 µm wavelength range [1]. The GaInNAs alloy grown on GaAs has been predicted to extend over that wavelength range with several material advantages. Due to a large bandgap bowing, small amounts of nitrogen in GaAs have drastic electronic effects reducing the bandgap greater than 100 meV per atomic percent of nitrogen. Mixed with InGaAs, long wavelength light emission is possible nearly lattice- matched to GaAs. With a larger conduction band offset than InP, GaInNAs quantum wells on GaAs are thought to have improved in thermal properties. Furthermore, being based on GaAs substrates, one can take advantage of well-established processing techniques and a superior Distributed Bragg Reflector (DBR) mirror technology. GaInNAs has shown encouraging characteristics at long wavelengths, including low threshold current densities, high temperature CW operation and high To in the wavelength range of 1.1-1.3 µm [2-4]. However, growing high quality GaInNAs material beyond 1.3 µm has proved challenging. Due to the low solubility of nitrogen in GaAs, nitrogen content needs to be minimized such that phase segregation does not occur. High indiu
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