Semi-Insulating, Fe-Doped Buffer Layers Grown by Molecular Beam Epitaxy

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Semi-insulating GaN(Fe) films grown by molecular beam epitaxy (MBE) were characterized by measuring electrical properties, deep-level spectra, Fe distribution profiles, microcathodoluminescence (MCL) spectra, electron-beam-induced current, and MCL imaging. The films were high-quality GaN(Fe) with Fe concentration from . The resistivity of GaN(Fe) buffers was , with the Fermi level pinned near . The buffer quality was characterized for Si-doped GaN and transistor structures grown by MBE on GaN(Fe). In contrast to the reported results for growth by metallorganic chemical vapor deposition, Fe distribution profiles did not show long tails extending into the layers grown on top of GaN(Fe). No features attributed to Fe were observed in lightly doped n-GaN grown on GaN(Fe) buffers. The n-GaN films showed electron mobility of . transistor structures grown on GaN(Fe) buffers showed two-dimensional electron gas mobility at , with a sheet density and a good pinch-off and a low interdevice leakage.