Suzuki, Toshi-kazu | Search NASA

DOE OSTI2016

Low-frequency noise in AlTiO/AlGaN/GaN metal-insulator-semiconductor heterojunction field-effect transistors

Using aluminum titanium oxide (AlTiO, an alloy of Al{sub 2}O{sub 3} and TiO{sub 2}) 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.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2014

Gate-control efficiency and interface state density evaluated from capacitance-frequency-temperature mapping for GaN-based metal-insulator-semiconductor devices

We present an analysis method for GaN-based metal-insulator-semiconductor (MIS) devices by using capacitance-frequency-temperature (C-f-T) mapping to evaluate the gate-control efficiency and the interface state density, both exhibiting correlations with the linear-region intrinsic transconductance. The effectiveness of the method was exemplified by application to AlN/AlGaN/GaN MIS devices to elucidate the properties of AlN-AlGaN interfaces depending on their formation processes. Using the C-f-T mapping, we extract the gate-bias-dependent activation energy with its derivative giving the gate-control efficiency, from which we evaluate the AlN-AlGaN interface state density through the Lehovec equivalent circuit in the DC limit. It is shown that the gate-control efficiency and the interface state density have correlations with the linear-region intrinsic transconductance, all depending on the interface formation processes. In addition, we give characterization of the AlN-AlGaN interfaces by using X-ray photoelectron spectroscopy, in relation with the results of the analysis.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗