Original Publication Date
Journal of Applied Physics
DOI of Original Publication
Date of Submission
Electronic noise has been investigated in AlxGa1−xN/GaN modulation-doped field-effect transistors of submicron dimensions, grown by molecular beam epitaxy techniques. Some 20 devices were grown on a sapphire substrate. Conduction takes place in the quasi-two-dimensional (2D) layer of the junction (xy plane) which is perpendicular to the triangular quantum well (z direction). A nondoped intrinsic buffer layer separates the Si-doped donors in the AlxGa1−xN layer from the 2D transistor plane. Since all contacts must reach through the AlxGa1−xN layer to connect internally to the 2D plane, parallel conduction through this layer is a feature of all modulation-doped devices. The excess noise has been analyzed as a sum of Lorentzian spectra and 1/fαnoise. The Lorentzian noise is ascribed to trapping of the carriers in the AlxGa1−xN layer. The trap depths have been obtained from Arrhenius plots of log(τT 2)versus 1000/T. Comparison with previous noise results for GaAs devices shows that: (a) many more trapping levels are present in these nitride-based devices and (b) the traps are deeper (farther below the conduction band) than for GaAs, as expected for higher band-gap materials. Furthermore, the magnitude of the noise is strongly dependent on the level of depletion of the AlxGa1−xN donor layer. We also note that the trap-measured energies are in good agreement with the energies obtained by deep level transient spectroscopy.
Duran, R. S., Larkins, G. L., Van Vliet, C. M., et al. Generation–recombination noise in gallium nitride-based quantum well structures. Journal of Applied Physics 93, 5337 (2003). Copyright © 2003 AIP Publishing LLC.
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VCU Electrical and Computer Engineering Publications