High-field quasi-ballistic transport in AlGaN/GaN heterostructures

Abstract

Mechanisms of electron transport formation in 2D conducting channels of AlGaN/GaN heterostructures in extremely high electric fields at 4.2 K have been studied. Devices with a narrow constriction for the current flow demonstrate high-speed electron transport with an electron velocity of 6.8 × 107 cm/s. Such a velocity is more than two times higher than values reported for conventional semiconductors and about 15% smaller than the limit value predicted for GaN. Superior velocity is attained in the channel with considerable carrier reduction. The effect is related to a carrier runaway phenomenon. The results are in good agreement with theoretical predictions for GaN-based materials.

Effects of light illumination on electron velocity of AlGaN/GaN heterostructures under high electric field

“…However, the measured saturation drift velocities show a much lower value of the order of 1:0 Â 10 7 cm=s, 5-7 although the highest electron velocity of 6:8 Â 10 7 cm=s was reported very recently in the ballistic transport regime. 8 One of important reasons for the unsatisfactory velocity is the hot phonon effect. Since the LO phonon lifetime ($0.35-2.5 ps) is much longer than the spontaneous LO phonon emission time ($10 fs) in GaN, 9 large numbers of non-equilibrium LO phonons would accumulate.…”

Density-dependent electron transport and precise modeling of GaN high electron mobility transistors

“…I-shaped test structure consisting of wide contact/access regions and a thin constriction defined by mesa isolation (of depth 100 nm) was used to investigate the velocity field characteristics (Figure 2). Due to the geometry of this device, the resistance from the ohmic/access regions is significantly lower (at least 14X) than that from the constriction 14,15 . Therefore it can be assumed that entire potential drop and current limiting mechanisms are related to the constriction.…”

Negative Differential Resistance Observation and a New Fitting Model for Electron Drift Velocity in GaN-Based Heterostructures

“…Characteristics of sample A with sample dimensions of 20 × 20 μm was measured by Guo et al [23] using an 80-ns pulsewidth and saturation velocity is 1.30 × 10 7 cm/s at 120 kV/cm. Danilchenko et al [21] reported that measured saturation velocity of an AlGaN/GaN heterostructure (sample B) with 100 × 10 μm using 30-ns pulsewidth is 1.1 × 10 7 cm/s at 80 kV/cm. Characteristics of sample C, sample D, and sample E were measured by Ardaravičius et al [20], [22] in different studies.…”

“…In another a paper, the reached applied electric field for an Al 0.33 Ga 0.67 N/AlN/GaN heterostructure was reported as 200 kV/cm [20]. In spite of Monte Carlo simulations assert a negative differential resistance (NDR) phenomenon for v d -E characteristics in this field range, it has been not observed exactly in the previous experimental studies [21].…”