As a promising candidate for AlGaN barrier, InAlN-based nitride heterostructures offer a unique opportunity to develop high frequency and high power electronic device, and have been extensively studied in the past five years. In this work, high quality nearly lattice-matched InAlN/GaN heterostructures were successfully grown on sapphire by pulsed metal organic chemical vapor deposition (PMOCVD) based on series optimization of growth parameters, such as growth temperature and pressure, pulse duration and waveform. Simultaneously, the epitaxial growth and material characterization of InAlN/GaN heterostructures give a further understanding of growth mechanism and provide a useful guide to achieve high quality to satisfy diversity of requirements.  In addition, high electron mobility transistors (HEMTs) are fabricated on this PMOCVD-grown nearly lattice-matched InAlN/GaN heterostructures, which exhibit a high 2DEG density of 2.15×10¹³ cm^-2 and electron mobility of 972 cm²/Vs for the barrier thickness of 13 nm measured by Hall effect in Van der Pauw configuration at room temperature. The processed HEMTs with gate dimensions of (0.5×50)×2 μm² and source-drain spacing of 3.5 μm provide a maximum drain current of 1279 mA/mm, a maximum extrinsic transconductance of 308 mS/mm, and current gain and maximum oscillation cutoff frequencies of 18 GHz and 27 GHz, respectively. For comparison, we also fabricated a conventional AlGaN/GaN HEMT with the same gate geometry and device process, which shows lower maximum drain current of 875 mA/mm and extrinsic transconductance of 198 mS/mm. The remarkably improved device performance is ascribed to the higher sheet carrier density and relatively thinner barrier thickness compared to AlGaN/GaN heterostructures. The obtained results demonstrate the promising potential of PMOCVD approach for applications in InAlN-related electronics’ epitaxy. Aggressive shrinking of gate length by adopting advanced electron beam lithograph and reduction of Ohmic contact resistance by optimization of Ohmic contact metals and annealing conditions can be pursued and applied to the future device process to further improve the device characteristics including output drain current density and operation frequency.  

1. PRESENTATION: Pulsed metal organic chemical vapor deposition growth, fabrication, and characterization of nearly lattice-matched InAlN/GaN high electron mobility transistors on sapphire substrate, Microsoft Office Document, 0.5MB

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1. Investigation of TMIn pulse duration effect on the properties of InAlN/GaN heterostructures grown on sapphire by pulsed metal organic chemical vapor deposition