Using aluminum titanium oxide (AlTiO, an alloy of Al2O3 and TiO2) as a high-k gate insulator, we fabricated and investigated AlTiO/AlGaN/GaN metal-insulator-semiconductor heterojunction field-effect transistors. From current low-frequency noise (LFN) characterization, we find Lorentzian spectra near the threshold voltage, in addition to 1/f spectra for the well-above-threshold regime. The Lorentzian spectra are attributed to electron trapping/detrapping with two specific time constants, ∼25 ms and ∼3 ms, which are independent of the gate length and the gate voltage, corresponding to two trap level depths of 0.5–0.7 eV with a 0.06 eV difference in the AlTiO insulator. In addition, gate leakage currents are analyzed and attributed to the Poole-Frenkel mechanism due to traps in the AlTiO insulator, where the extracted trap level depth is consistent with the Lorentzian LFN.
We have systematically investigated low-frequency noise (LFN) in InAs films with several thicknesses (≃10-100 nm) bonded on low-k flexible substrates (InAs/FS), comparing with that in InAs films epitaxially grown on GaAs(001) substrates (InAs/GaAs). We obtain current LFN spectra exhibiting approximate 1/f characteristics and consequent effective Hooge parameters α depending on the thickness, where we find that α in the InAs/FS is larger than that in the InAs/GaAs. The behavior of α can be attributed to the fluctuation of the electron mobility dominated by surface/interface charge scattering and by thickness fluctuation scattering.
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