Observation of Side-Gating Effect in AlGaN/GaN Heterostructure Field Effect Transistors

Abstract

The side-gating effect was demonstrated in AlGaN/GaN heterostructure field effect transistors (HFETs) for the first time. Using 10-µm-thick i-GaN buffer layers, drain currents decreased significantly with the application of a negative bias on a side gate 8 µm away from the FET. The transient responses with LED illumination demonstrated half-recovery condition that can be interpreted as a negative-charge redistribution through a hole emission from traps. The application of a positive side-gate bias confirmed the half-recovery mechanism. From the temperature variation measurements, the trap energy level is estimated to be 0.76 eV from the valence band with a hole capture cross section of approximately 4×10-16 cm2. All these results indicate that the side-gating effect is caused by hole traps in the i-GaN layer, which is in accord with the Shockley–Read–Hall model of deep traps.

Electrical Investigation of Turn-On Capacitance Recovery Characteristics in Carbon-Doped AlGaN/GaN Hetero-Structures Grown on Si Substrates

“…In this case, the depletion layers under the Schottky electrodes extend easily into the entire GaN:C buffer layers under the off-bias state. Additionally, considering that deep-level defects are generally located in the lower half of the bandgap, these defects in the GaN:C buffer layers behave as acceptor-like trapping centers and are negatively charged up even in the depletion layers formed under the off-bias stress at the V G of −30 V. 21 Additionally, these negative charges accumulated under the off-bias state should be neutralized by some way under the sequential turn-on state. The speed of the charge neutralization of the deep-level defects in the depletion layers under the turn-on state corresponds to the turn-on capacitance recovery characteristics.…”

Deep-Donor-Induced Suppression of Current Collapse in an AlGaN-GaN Heterojunction Structure Grown on Si

“…3 (a), this negatively charged state remains even at t = 5000 s, because the DA requires a longer time to recover from the negative charged state owing to the deep E DA . This is the origin of the current collapse typically observed in AlGaN/GaN-HFETs [9]. However, this transient behavior does not appear in the DD-rich model, because a negative V GS consequently stimulates electron emission from DDs, the charge state of which transforms from neutral to positive, denoted as 0 → + in the inserted band diagram of Fig.…”

“…The DA captures externally injected electrons by the biases, resulting in a negatively charged film. This charge-state transition with its large time constant owing to a large E DA yields the so-called current collapse, which is a chronic problem in AlGaN/GaN HFETs [9]. Therefore, this problem must be resolved for not only improving device performance but also for assuring reliability [10].…”

Extraction of net acceptor type trap density in semi-insulating GaN layers grown on Si substrate by DC I-V measurement

“…The N T – N D of semi‐insulating GaN layers is an important parameter to determine the performance of AlGaN/GaN HFETs. A certain quantum of N T – N D reportedly plays an essential role to suppress the punch‐though in short channel , and capture electrons, causing current collapse, which is a common problem with AlGaN/GaN HFETs . Therefore, the N T – N D of semi‐insulating GaN layers must be quantitatively estimated in order to simulate and control HFET's characteristics, and to monitor the epitaxial growth process of AlGaN/GaN structures in manufacturing.…”