Degradation and phase noise of InAlN/AlN/GaN heterojunction field effect transistors: Implications for hot electron/phonon effects

Abstract

In15.7%Al84.3%N/AlN/GaN heterojunction field effect transistors have been electrically stressed under four different bias conditions: on-state-low-field stress, reverse-gate-bias stress, off-state-high-field stress, and on-state-high-field stress, in an effort to elaborate on hot electron/phonon and thermal effects. DC current and phase noise have been measured before and after the stress. The possible locations of the failures as well as their influence on the electrical properties have been identified. The reverse-gate-bias stress causes trap generation around the gate area near the surface which has indirect influence on the channel. The off-state-high-field stress and the on-state-high-field stress induce deterioration of the channel, reduce drain current and increase phase noise. The channel degradation is ascribed to the hot-electron and hot-phonon effects.

Degradation in AlGaN/GaN heterojunction field effect transistors upon electrical stress: Effects of field and temperature

“…Thus, the degradation mechanism(s) associated with the on-statehigh-field stress is not simply due to the high electric field, but to the electric field induced hot-electron, hot phonon, and self-heating effects in aggregate as demonstrated in the degradation of InAlN/GaN based HFETs. 8 And further evidence comes from the gate leakage current ratios of stressed to pristine devices under these two different stress types as demonstrated in Fig. 3, where larger gate leakage current ratios correspond to larger gate-drain stress voltages for each stress type.…”

“…Previously, stress under different bias points has been applied to study the impact of various effects on the degradation of nearly lattice-matched InAlN/GaN HFETs using the low frequency noise technique, where the inverse-piezoelectric effect has been demonstrated to be much less important than the hot-electron/phonon effects. 8 However, the behavior in AlGaN/GaN HFETs may be more complicated due to the large strain in pseudomorphically grown AlGaN barrier layer as well as the still relatively large drain current. In this paper, we measure the phase noise and DC characteristics to investigate the degradation mechanisms in passivated AlGaN/GaN HFETs stressed under various bias points encompassing on-state-high-field and reverse-gate-bias and elevated temperatures in an effort to interrogate the various degradation mechanisms.…”

“…Interaction of the huge amount of hot electrons in the channel with the lattice induces self-heating (equilibrium excess acoustic phonons) and hot phonon (non-equilibrium optical phonon) effects. 8,13 Comparing the noise spectra in Figs. 1 and 2, we can clearly see that the degradation behavior is quite different.…”

Hot-Phonon Effects on High-Field Transport in GaN and AlN

“…Later, Ramonas et al [8] included these effects, though their study was limited to the applied electric fields up to 14 kV/cm. Recent work has proposed that hot electrons may be responsible for the degradation of AlGaN/GaN and InAlN/GaN HFET's at larger applied fields [9], with electron temperatures measured experimentally at 2600 and 5000 K, respectively [10]. While such high temperatures may be highly localized, it is clear that the hot-phonon effects cannot be neglected.…”

Hot electron induced non-saturation current behavior at high electric field in InAlN/GaN heterostructures with ultrathin barrier

“…On one hand, compared to AlGaN, the material quality of InAlN still need to be improved due to the different optimized growth conditions of InN and AlN and the expected large immiscibility gap of the ternary alloy. Thus, there are large density of defects which may correlate to the problem of more serious degradation of the InAlN/GaN HEMTs678. On the other hand, the larger spontaneous polarization in InAlN/GaN heterostructures contributes to much higher two-dimensional electron gas (2DEG) density in the lattice-matched In 0.18 Al 0.82 N/GaN system with thin barrier layer910.…”