DC And RF Characterization Of n-GaN Schottky Diode For Microwave Application
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Date
2011-01
Authors
Munir, Tariq
Journal Title
Journal ISSN
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Publisher
Universiti Sains Malaysia
Abstract
Gallium nitride is a promising wide bandgap semiconductor material for high-power, high temperature and high frequency device applications. However, there are still a number of factors that are limiting the material to reach a satisfactory device performance. Among them the most important and critical factors are the reverse leakage current, series resistance, junction capacitance and thermal stability that limits Schottky diode performance on gallium nitride for Direct Current (DC) and Radio Frequency (RF) characteristics. To overcome these limitations we studied the influence of metal contact, contact area, thermal behavior and edge termination on DC and RF characteristics of n-GaN Schottky diode by simulation and fabrication approach.
For metal contact study we simulate and fabricate n-GaN Schottky diode using wide variety of single metal Platinum(Pt), Nickel(Ni), Palladium (Pd), and bilayer Schottky metals Platinum/Palladium(Pt/Pd), Platinum/Nickel(Pt/Ni), and Platinum/Titanium(Pt/Ti) annealed from room temperature up to 800ºC while Aluminum/Titanium (Al/Ti) for ohmic contact annealed from room temperature up to 900ºC, to study the reverse leakage current, thermal stability and insertion losses using various techniques such as current-voltage (I-V),capacitance-voltage (C-V), Scanning electron microscope (SEM),X-ray diffraction (XRD) and Scattering parameters (S-parameters) for DC and RF characteristics. Studies shows that Platinum/Palladium (Pt/Pd) bilayer Schottky metal are the best choice for DC characteristics among other Schottky metals due to Ga vacancies formation at the Schottky interface area showing lower reverse leakage current, better thermal stability up to 800ºC at elevated temperatures. The frequency response of simulated Schottky metal behave as high pass filter while fabricated contact behaves like notch filter (maximum impedance at resonant frequency) due to stray capacitance and series resistance (skin effect). In general, Pt/Pd bilayer shows lower insertion loss compared to other Schottky metal for RF characteristics while Al/Ti as ohmic contact shows improved linear (I-V) characteristics due to TiN interfacial layer formation and high thermal stability up to 900ºC due to Al and Ti alloys formation.
Thermal behaviors of n-GaN Schottky diode were studied from room temperature to 900ºC. The Study shows that breakdown voltage reduced and insertion loss increases with temperature increase due to phonon assisted tunneling and free electron generation across the junction contact area.
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Keywords
Schottky diode performance on gallium nitride for , Direct Current (DC) and Radio Frequency (RF) characteristics