Defect characterization of heavy ion irradiated AllnN/GaN on Si high-electron-mobility transistors

Abstract

The characteristic energies of traps in InAlN/AlN/GaN high-electron mobility transistor structures on Si(111) substrates formed after irradiation with 75 MeV S-ions are studied by means of c-lattice parameter analysis, vertical IV-characteristics, micro-photoluminescence (μ-PL), photocurrent (PC) and thermally stimulated current (TSC) spectroscopy. From the lattice parameter analysis, point defect formation is concluded to be the dominant source of defects upon irradiation. A strong compensation effect manifests itself through enhanced resistivity of the devices as found in vertical IV-measurements. Defect formation is detected optically by an additional PL-band within the green spectral region, while defect states with threshold energies at 2.9 eV and 2.65 eV were observed by PC spectroscopy. The TSC spectra exhibit two defect-related emissions between 300 K and 400 K with thermal activation energies of 0.78–0.82 eV and 0.91–0.98 eV, respectively. The data further supports the formation of Ga vacancies (VGa) and related complexes acting mainly as acceptors compensating the originally undoped n-type GaN buffer layers after irradiation.