Abstract
AlGaN/GaN Schottky barrier diodes (SBDs) with high Al composition and high temperature atomic layer deposition (ALD) Al2O3 layers were investigated. Current–voltage (I–V), X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), and capacitance–voltage (C–V) measurements were conducted in order to find the leakage current mechanism and reduce the reverse leakage current. The fabricated AlGaN/GaN SBDs with high Al composition exhibited two orders’ higher leakage current compared to the device with low Al composition (20%) due to large bulk and surface leakage components. The leakage current measured at −60 V for the fabricated SBD with Al2O3 deposited at temperature of 550 °C was decreased to 1.5 μA, compared to the corresponding value of 3.2 mA for SBD with nonpassivation layer. The high quality ALD Al2O3 deposited at high temperature with low interface trap density reduces the donorlike surface states, which effectively decreases surface leakage current of the AlGaN/GaN SBD.
Highlights
Measurements were conducted in order to find the leakage current mechanism and reduce the reverse leakage current
The high quality atomic layer deposition (ALD) Al2 O3 deposited at high temperature with low interface trap density reduces the donorlike surface states, which effectively decreases surface leakage current of the AlGaN/GaN SBD
The leakage current of the SBD without passivation layer was as high as 3.2 mA at
Summary
Measurements were conducted in order to find the leakage current mechanism and reduce the reverse leakage current. Due to the superior material properties such as wide bandgap and high electron peak velocity, AlGaN/GaN devices exhibit high breakdown voltage and very fast switching speed. Their advantages are very important to adopt high power switching systems, including converters and inverters for heavy motors, electric vehicles, and ships [4,5,6], in order to reduce the size of the whole power systems caused by simplifying the power conversion system. The high Al composition in AlGaN/GaN heterostructure is appropriate, thanks to higher 2DEG density and larger on-current It deteriorates the reverse leakage currents related to large density of the surface states [7]. These surface states are strongly involved in the severe current collapse of the AlGaN/GaN-based devices, which considerably degrades the device reliability plus the device performance [8,9,10]
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