Growth and Characterization of InGaNAs Quaternary Alloys for the Fabrication of Long Wavelength MSM Photodetectors on Ga
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Growth and Characterization of InGaNAs Quaternary Alloys for the Fabrication of Long Wavelength MSM Photodetectors on GaAs Substrates Erle Higgins, Julian Noad, Francois Gouin, and David Coulas Communication Research Center Canada Ottawa, Ontario, Ca K2H 8S2 ABSTRACT In this paper, the optical and electrical properties of both as-grown and annealed thick InxGa1-xNyAs1-y layers grown by metal organic chemical vapour deposition (MOCVD) are presented. Through careful control of the trimetylyindium (TMIn), dimetylyhydrazine (DMHy), trimrthylgallium (TMGa) and arsine (AsH3) precursors, lattice matching conditions were achieved for epitaxial layers containing up to 3% nitrogen (0≤y≤0.03) and 11% indium (0≤x≤0.11) with bandgap wavelengths to 1.3 µm. Nomarski optical microscopy and double crystal x-ray diffraction (XRD) measurements are used to investigate surface morphology, material quality and lattice-matched conditions. There is little or no 10K photoluminescence from the as-grown layers; alloy activation through rapid thermal annealing must be performed to obtain observable photoluminescence peaks. Annealing is also performed to reduce the resistivity of the as-grown layers. Once annealed the undoped layers exhibited ptype carrier concentrations of 5.5x1017 cm-3 and mobilities of 50 cm2/Vs. The DC and frequency response performance characteristics of metal-semiconductor-metal (MSM) photodetectors fabricated on both as-grown and annealed InGaNAs materials are examined and compared to similar structures fabricated using GaAs and InGaAs/InP epitaxial materials. INTRODUCTION Dilute nitride III-V materials such as GaNAs and InGaNAs have been the focus of much theoretical and experimental research activity over the last few years [1,2]. In particular, the quaternary alloy system, InGaNAs, which can have a bandgap wavelength in excess of 1.5 µm and be lattice-matched to GaAs substrates [3,4], offers the potential of complex multifunction “all-GaAs” optoelectronic integrated circuits. “All-GaAs” long wavelength OEICs based on dilute nitrides such as InGaNAs will benefit from an increased electronic and optical functionality, smaller size and lower assembly and packaging costs as well as improved reliability and lower part counts. Potential applications of these “all-GaAs” devices and circuits range from components for use in metro, wide area (WAN) and local area (LAN) communication networks to microwave signal distribution in satcom applications such as large space-based phased array antennas. High-speed photodetectors suitable for long haul, metro or wide area broadband networks often require more demanding material characteristics than other optoelectronic devices. For example, while lasers and LEDs can be inherently slow, they can still be operated in DC mode and combined with external modulators to produce high-speed signals. Photodetectors on the other hand must have both a high responsivity and be extremely fast, with typical bandwidths of 5-10 GHz, if they are to meet the requirements of 10 Gb/s systems.
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