Window for better reliability of nitride heterostructure field effect transistors

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

“…13 cm -2 in the standard GaN 2DEG channel at the optimum bias for the cut-off frequency) is consistent with the condition for ultrafast decay of hot phonons [17].…”

“…The signature of the LO-phonon-plasmon crossover manifests itself in experiments on electron drift velocity [10], transistor cut-off frequency [18], and transistor degradation: the electron drift velocity is the highest, the transistor operation is the fastest, the phase noise level is the lowest, and the device degradation is the slowest inside the electron density window where the hotphonon lifetime acquires the shortest values [17,19].…”

“…The alloy-free coupled {GaN/AlN/GaN} channel is promising for its improved low-field transport properties. 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]).…”

Characterization of Ag Schottky Barriers on Be0.02Mg0.26ZnO/ZnO Heterostructures

“…Performance of such devices at high electric field, where electron transport is highly controlled by longitudinal optical (LO) phonons, suffers due to accumulation of non‐equilibrium hot LO phonons owing to strong electron–LO phonon coupling. Devices operating at or near plasmon–LO phonon resonance exhibit high electron drift velocity allowed by ensuing ultrafast decay of hot LO phonons, which leads to faster electron energy relaxation and optimum device operation conditions (higher frequencies, lower degradation) . Plasmon–LO phonon resonance occurs when the energy of the LO phonon becomes similar to the plasmon energy, which occurs in ZnO at a bulk carrier concentration of ≈7 × 10 18 cm −3 (ZnO LO phonon energy 72 meV) .…”

High-field electron transport in bulk ZnO

“…Because the high-field electron transport is accompanied with intense LO-phonon emission by hot electrons, the emitted non-equilibrium LO phonons accumulate, and the associated phenomena are often referred to as hot-phonon effects. In general, hot phonons play an important role in devices operated at high electric fields such as microwave and high power field-effect transistors because of pivotal role they play in heat dissipation and device reliability [6]. The fastest decay of hot phonons takes place in the vicinity of plasmon-LO-phonon resonance [7].…”