Separation of hot-electron and self-heating effects in two-dimensional AlGaN/GaN-based conducting channels

Abstract

We address experimental and theoretical study of a two-dimensional electron gas transport at low and moderate electric fields. The devices under study are group-III nitride-based ͑AlGaN/GaN͒ gateless heterostructures grown on sapphire. The transmission line model patterns of different channel lengths, L, and of the same channel width are used. A strong dependence of the device I-V characteristics on the channel length has been found. We have developed a simple theoretical model to adequately describe the observed peculiarities in the I-V characteristics measured in steady-state and pulsed (10 Ϫ6 s) regimes. The effect of the Joule heating of a heterostructure is clearly distinguished. The thermal impedance and the channel temperature rise caused by the Joule self-heating have been extracted for the devices of different L at different values of dissipated power. The current reduction due to both self-heating and hot-electron effects is determined quantitatively as a function of the electric field.

Power and temperature dependence of low frequency noise in AlGaN∕GaN transmission line model structures

“…A detailed description of samples can be found elsewhere. 3 We used samples with channel length of 10, 15, 20, 25, 30, and 35 m. The applied voltage was varied in the range from 0.01 to 10 V, the maximal value of measured current did not exceed 112 mA. The noise spectra were measured in the frequency range from 1 Hz to 100 kHz.…”

“…At the same time, the characteristic times obtained from the noise measurements are significantly longer than heat relaxation times estimated from our experiments. 3 Therefore, another factor determining the transient frequency should be considered. A more probable mechanism is coupling between surface and channel systems, which leads to redistribution of electron density along the channel under applied voltage.…”

“…In HEMTs the self-heating effects reduce the 2D electron mobility and cause sublinearity in the current-voltage characteristics (CVC) of the device. 3 Moreover, the nonuniformity of the electric field applied to the channel due to lateral redistribution of charge on the surface or in the barrier also results in an increased channel resistance. 4 To investigate the above mentioned effects, transmission line model (TLM) structures are most suitable.…”

The Electric Field and Temperature Dependence of Conductance of Two-Dimensional Electron Gas in AlGaN/AlN/GaN

“…Some processes, that could influence 2DEG sheet density, have been pointed out which can be observed in nanosecond time scale of conductance relaxation. Among these are: (1) self heating and its cooling down after the electric field pulse [2]; (2) transfer and trapping of hot carriers from 2DEG channel to either AlN spacer or GaN buffer layer which contains high concentration of deep traps and subsequent release [3]; (3) electric field and temperature influence on spontaneous and piezoelectric polarization [4]. Trapping effects with characteristic times lying within 5 ÷ 10 µs have been indicated [5].…”

Self-heating effects in AlGaN/GaN HEMT heterostructures: Electrical and optical characterization

“…The broad spectrum of experimental and theoretical methods were used for temperature estimations in 2DEG conducting channel and heterostructures at whole: electrical DC and pulse measurements [4][5][6], micro-Raman and infrared (IR) Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 4.…”