Comparison of different surface passivation dielectrics in AlGaN/GaN heterostructure field-effect transistors

Abstract

Different dielectrics were used for post-processing surface passivation of AlGaN/GaN heterostructure field-effect transistors (HFETs) and the resulting electrical characteristics examined. An increase in the maximum drain current of approximately 25% was observed after Si3N4 and SiO2 deposition and ~15% for annealed SiO on AlGaN/GaN HFETs. In all cases, the passivation was found to increase the gate leakage current with an observed reduction in the leakage activation energy. However, the rise in gate leakage current was least for SiO. The plasma enhanced chemical vapour deposition method was found not to contribute to the passivation mechanism, whilst the presence of Si appears to be an important factor.

Analysis of DC–RF Dispersion in AlGaN/GaN HFETs Using RF Waveform Engineering

“…GaN devices have been shown to be highly sensitive to different surface preparation and passivation techniques, suggesting that trapped surface charge has a significant role in the dispersion [7].…”

“…In order to reduce current collapse, refinements in layer structure as well as improved device processing techniques will likely be required. A number of device processing approaches, including various passivation, fieldplate, gate recess and surface cap strategies, have already been employed in an effort to mitigate the detrimental effects of the trapped surface charge [7] [15][16][17]. In many GaN processes these approaches have only led to partial success, and consequently measurement techniques that provide insight into the trap phenomena and can quantify device performance have been developed to help device designers produce better devices with less dispersion.…”

Electrical characteristics of AlGaN/GaN metal-insulator semiconductor heterostructure field-effect transistors on sapphire substrates

“…The SiO-MISHFET devices were also fabricated but exhibit poorer performance compared to its SiO 2 counterparts; this is attributed to the inferior dielectric/AlGaN interface quality. 9 The decrease in transconductance for the MISHFETs is consistent with the larger separation between the MISHFET channel and the gate. Because of the larger gate to channel separation of the MISHFETs, the pinch-off voltage was extended to Ϫ9 V from the Ϫ4 V observed in unpassivated HFETs.…”

Effect of electron-beam irradiation on leakage current of AlGaN/GaN HEMTs on sapphire

“…AlGaN/GaN based HEMTs have been widely studied for the application of the power semiconductor devices due to their excellent high field electron transport properties and high-breakdown electric field [2]. However, the device performance and reliability of conventional AlGaN/GaN HEMTs have been significantly limited due to a high gate leakage current [3].…”