Plasmon-enhanced heat dissipation in GaN-based two-dimensional channels

Abstract

Decay of nonequilibrium longitudinal optical ͑LO͒ phonons is investigated at room temperature in two-dimensional electron gas channels confined in nearly lattice-matched InAlN/AlN/GaN structures. A nonmonotonous dependence of the LO-phonon lifetime on the supplied electric power is reported for the first time and explained in terms of plasmon-LO-phonon resonance tuned by applied bias at a fixed sheet density ͑8 ϫ 10 12 cm −2 ͒. The shortest lifetime of 30Ϯ 15 fs is found at the power of 20Ϯ 10 nW/ electron.

Electron transport in a coupled GaN/AlN/GaN channel of nitride HFET

“…The highest value is reached at ~(1.0±0.1)×10 13 cm -2 electron density in agreement with the resonance decay of hot phonons (non-equilibrium longitudinal optical (LO) phonons): the resonance takes place in the vicinity of the crossover of dispersion curves for initially noninteracting LO phonons and plasmons. The plasmonassisted decay of LO phonons has been confirmed experimentally [11][12][13]. For GaN-based 2DEG channels the hot LO phonon lifetime is the shortest near…”

“…While the low-field electron mobility tends to decrease as the density of 2DEG increases, the high-field drift velocity is not a monotonous function of the density [10]. The highest value is reached at ~(1.0±0.1)×10 13 cm -2 electron density in agreement with the resonance decay of hot phonons (non-equilibrium longitudinal optical (LO) phonons): the resonance takes place in the vicinity of the crossover of dispersion curves for initially noninteracting LO phonons and plasmons. The plasmonassisted decay of LO phonons has been confirmed experimentally [11][12][13].…”

“…When the pristine electron density exceeds the resonance value, the resonance can be tuned in with a variable negative bias applied to the gate of a nitride HFET [17]. The HFET with a pristine 2DEG density of 1.75×10 13 cm -2 in the alloy-free coupled GaN/AlN/GaN channel demonstrates the optimal frequency performance in terms of electron velocity (f T = 8.6 GHz for L g = 1 μm; V DS = 15 V, where L g is gate length, and V DS is drain-source voltage) at a relatively low gate bias of V GS = -1.75 V, while single-channel HFETs typically require a higher gate bias (-2.9 V at 1.75×10 13 cm -2 [28]). Among other advantages, the ability to tune into the resonance with a lower gate bias is potentially useful for reducing gate leakage currents.…”

Signature of Hot Phonons in Reliability of Nitride Transistors and Signal Delay

“…The fluctuation technique [8] was applied to GaN--based 2DEG channels and yielded the lifetime in a wide range of electron sheet densities [3,4,9]. The non--monotonous dependence was revealed at low electric fields ( Fig.…”

“…Resonance dependence of hot-phonon lifetime on carrier density at low electric field. SquaresRaman data (top scale) [6], circles and down-triangle -fluctuation technique (bottom scale) [4,8,9], up--triangle -intersubband absorption (bottom) [10], dashed curve -plasmon-LO-phonon model (top) [7], solid curve -Eq. (1) (bottom).…”