Abstract
The buffer and surface trapping effects on low-frequency (LF) Y-parameters of Fe-doped AlGaN/GaN high-electron mobility transistors (HEMTs) are analyzed through experimental and simulation studies. The drain current transient (DCT) characterization is also carried out to complement the trapping investigation. The Y22 and DCT measurements reveal the presence of an electron trap at 0.45–0.5 eV in the HEMT structure. On the other hand, two electron trap states at 0.2 eV and 0.45 eV are identified from the LF Y21 dispersion properties of the same device. The Y-parameter simulations are performed in Sentaurus TCAD in order to detect the spatial location of the traps. As an effective approach, physics-based TCAD models are calibrated by matching the simulated I-V with the measured DC data. The effect of surface donor energy level and trap density on the two-dimensional electron gas (2DEG) density is examined. The validated Y21 simulation results indicate the existence of both acceptor-like traps at EC –0.45 eV in the GaN buffer and surface donor states at EC –0.2 eV in the GaN/nitride interface. Thus, it is shown that LF Y21 characteristics could help in differentiating the defects present in the buffer and surface region, while the DCT and Y22 are mostly sensitive to the buffer traps.
Highlights
The Y21 results may be useful for controlling the buffer and surface trapping phenomena in the commercial microwave AlGaN/GaN high-electron mobility transistors (HEMTs)
The drain current transient (DCT) spectroscopy is a powerful tool to examine the temporal evolution of the carrier trapping and de-trapping phenomena in the GaN HEMT [8,9,10,11,12,13,14,15,16,17,18]
The drain-lag filling pulse indicates that VDS is switched from 10 to 20 V for 100 ms during the initial trap-filling phase, and it is changed again to 10 V, while VGS is maintained at a fixed bias to obtain the IDS = ≈50 mA/mm; it can be called drain-lag DCT spectroscopy [2,7,34]
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The drain current transient (DCT) spectroscopy [8,9,10,11,12,13,14,15,16,17,18] and low-frequency (LF) output-admittance (Y22 ) parameters [15,16,19,20,21,22,23,24,25,26,27] are the well-estimated techniques to characterize the deep-level defects present in the AlGaN/GaN HEMT structures. The Y21 results may be useful for controlling the buffer and surface trapping phenomena in the commercial microwave AlGaN/GaN HEMTs. Y22 and DCT spectroscopy of the HEMT are examined to complement the trapping investigation. The outcomes of this work are envisioned to provide an effective input to the GaN crystal growth community to improve the quality of the GaN/AlGaN/GaN structure layers
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