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Low-frequency noise technique was applied to analyze performance of nearly lattice-matched InAlN/AlN/GaN heterostructure field-effect transistors and their degradation caused by electrical stress. Nearly identical devices from the same wafer have undergone a 7 h DC electrical stress at a fixed DC drain bias of VDS = 20 V and different gate biases. We noted up to 32 dB/Hz higher low-frequency noise for stressed devices over the entire frequency range of 1 Hz-100 kHz. The measurements showed the minimum degradation at a gate-controlled two-dimensional electron gas density of 9.4 × 1012 cm−2. This result is in good agreement with the reported stress effect on drain-current degradation and current-gain-cutoff-frequency measurements and consistent with the ultrafast decay of hot-phonons due to the phonon–plasmon coupling.

Experimental investigation of electron transport along a two-dimensional channel confined in an InGaN alloy of Al 0.82 In 0.18 N/AlN/In 0.1 Ga 0.9 N/GaN structure was performed at room temperature under near-equilibrium thermal-bath temperature. A soft damage was observed at a threshold electric field applied in the channel plane. The threshold current for soft damage and the supplied electric power were lower in the channels with a higher electron density. The results are interpreted in terms of plasmon-assisted heat dissipation. In agreement with ultra-fast decay of hot phonons in the vicinity of the resonance with plasmons, the electron drift velocity acquires a highest value of ∼2 × 10 7 cm s −1 at 180 kV cm −1 in channels with 1 × 10 13 cm −2 and decreases as the electron density increases. No negative differential resistance is observed. The effective hot-phonon lifetime is estimated as ∼ 2 ps at 1.6 × 10 13 cm −2 at low electric fields and is found to decrease as the field increases.

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