Comparative analysis of hot‐electron transport in AlGaN/GaN and AlGaN/AlN/GaN 2DEG channels

Abstract

Nanosecond‐pulsed current–voltage measurements were used to study hot‐electron transport in undoped AlGaN/GaN and AlGaN/AlN/GaN two‐dimensional electron gas channels biased up to 200 kV/cm. Voltage pulses of 1 ns were applied in order to minimize channel heating. The current saturated at 100 kV/cm in the AlN‐interbarrier‐contained structures; the estimated saturated drift velocity was about 1.1 × 107 cm/s. No saturation of the current was observed in AlGaN/GaN channels in the field range below 200 kV/cm. Monte Carlo simulation of hot‐electron transport was carried out with electron gas degeneracy and hot phonons taken into account. A fairly good fit of the experimental results with the Monte Carlo simulation data was obtained in the electric field range up to 30 kV/cm. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Strain dependent electron drift velocity in Al1–xInxN/AlN/GaN

“…We think that the random piezoelectric fields and defect density are reduced when the alloy composition is lattice matched with the GaN layer in the Al 0.82 In 0.18 N/AlN/GaN structure. A similar conclusion follows from a comparison of the experimental results for the LM AlInN/AlN/GaN 2DEG channel with those for strained AlGaN/GaN [10], AlGaN/GaN/AlN/GaN [11], and silicon-doped GaN [12] (see Fig. 4).…”

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

“…scattering does not play a significant role in camelback channels. Also, the maximum attained drift velocity in the alloy-free coupled channel exceeds that in a standard AlN-spacer single GaN-based 2DEG channel by 50% [4]. Despite the fact that the velocity in the coupled channel is twice lower than the maximum drift velocity measured in the single GaN 2DEG channel [7], for similar electron densities (6×10 12 cm -2 ) the velocity in the coupled channel is 50% higher than in the single GaN 2DEG channel [9].…”

“…4. Room temperature dependence of the drift velocity on the electric field for the alloy-free coupled {GaN/ AlN/GaN} channels (L = 5 μm, blue triangles; L = 2 μm, stars) and single AlN-spacer GaN-based 2DEG channel (L = 5 μm, diamonds [4]). Voltage pulse duration is 2 ns.…”

“…It is known from the Monte Carlo simulation [4] that the shorter the lifetime is, the faster hotphonon decay and the higher the electron velocity are. For the standard AlN-spacer single GaN-based 2DEG channel the phonon lifetime is longer (1 ps, [4]) even at high electric fields as compared to that in the coupled channel, and this causes the reduction in drift velocity (Fig. 4, diamonds).…”

“…The cut-off frequency is related to the average carrier velocity in a two-dimensional electron gas (2DEG) channel. The experimental reports show that the room temperature electron velocity values in GaN-based 2DEG channels lie between (1-3)×10 7 cm/s [3][4][5][6][7][8][9]. 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].…”