Abstract
This paper reports an improvement in Pt/n-GaN metal-semiconductor (MS) Schottky diode characteristics by the introduction of a layer of HfO2 (5 nm) between the metal and semiconductor interface. The resulting Pt/HfO2/n-GaN metal-insulator-semiconductor (MIS) Schottky diode showed an increase in rectification ratio from 35.9 to 98.9(@ 2V), increase in barrier height (0.52 eV to 0.63eV) and a reduction in ideality factor (2.1 to 1.3) as compared to the MS Schottky. Epitaxial n-type GaN films of thickness 300nm were grown using plasma assisted molecular beam epitaxy (PAMBE). The crystalline and optical qualities of the films were confirmed using high resolution X-ray diffraction and photoluminescence measurements. Metal-semiconductor (Pt/n-GaN) and metal-insulator-semiconductor (Pt/HfO2/n-GaN) Schottky diodes were fabricated. To gain further understanding of the Pt/HfO2/GaN interface, I-V characterisation was carried out on the MIS Schottky diode over a temperature range of 150 K to 370 K. The barrier height was found to increase (0.3 eV to 0.79 eV) and the ideality factor decreased (3.6 to 1.2) with increase in temperature from 150 K to 370 K. This temperature dependence was attributed to the inhomogeneous nature of the contact and the explanation was validated by fitting the experimental data into a Gaussian distribution of barrier heights.
Highlights
Attempts to sustain Moore’s law[1] have been spearheaded by continuous scaling of Si transistors for over 30 years
This paper reports an improvement in Pt/n-gallium nitride (GaN) metal-semiconductor (MS) Schottky diode characteristics by the introduction of a layer of HfO2 (5 nm) between the metal and semiconductor interface
We believe that HfO2 would play a positive role as an interfacial layer in GaN based Schottky diodes and it is important to understand the electrical properties of this Pt/HfO2/n-GaN interface to enable us to better utilise the possibilities offered by the combination of high-k dielectrics and III-nitride semiconductors
Summary
Attempts to sustain Moore’s law[1] have been spearheaded by continuous scaling of Si transistors for over 30 years. Schottky diodes[7] have advantages like high operating frequency, fast switching speed and low forward voltage drop. Schottky diodes are widely used in a variety of RF and microwave applications like varactors, detectors, mixers, multipliers and low-voltage reference circuits. There have been various studies on the metal-insulator-semiconductor Schottky barrier[8,9,10,11] in particular due to the advantages it offers like lower leakage current and higher rectification ratio. In the study of semiconductor surfaces, the metal-insulator-semiconductor Schottky diode is an important device. The GaN MIS structure has been studied[12,13,14,15] for its importance in switching devices where the presence of the insulator layer would provide lower leakage currents and reduce power consumption
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