Abstract
Atomic layer deposited AlGaN on GaN substrate with different thicknesses was prepared and the electron transport mechanism of AlGaN/GaN Schottky diodes was investigated. Above 348 K, both 5 and 10 nm thick AlGaN showed that the thermionic emission model with inhomogeneous Schottky barrier could explain the forward current transport. Analysis using a dislocation-related tunneling model showed that the current values for 10 nm thick AlGaN was matched well to the experimental data while those were not matched for 5 nm thick AlGaN. The higher density of surface (and interface) states was found for 5 nm thick AlGaN. In other words, a higher density of surface donors, as well as a thinner AlGaN layer for 5 nm thick AlGaN, enhanced the tunneling current.
Highlights
Among III-nitride materials, AlGaN/GaN heterostructures have gained much interest due to the applications in high-temperature, high-voltage, and high-frequency electronic devices [1,2,3].In particular, AlGaN/GaN-based high electron mobility transistors (HEMTs) are commonly used because two-dimensional electron gas (2DEG) located just below the AlGaN/GaN interface can be obtained with high conductivity
The large reverse leakage current occurring in AlGaN/GaN HEMTs increase the noise at low-frequency and leads to current collapse, limiting the applicability of such devices [4]
We characterized the current transport properties of AlGaN/GaN Schottky diodes with an atomic layer deposition (ALD)-grown AlGaN layer
Summary
Among III-nitride materials, AlGaN/GaN heterostructures have gained much interest due to the applications in high-temperature, high-voltage, and high-frequency electronic devices [1,2,3].In particular, AlGaN/GaN-based high electron mobility transistors (HEMTs) are commonly used because two-dimensional electron gas (2DEG) located just below the AlGaN/GaN interface can be obtained with high conductivity. Among III-nitride materials, AlGaN/GaN heterostructures have gained much interest due to the applications in high-temperature, high-voltage, and high-frequency electronic devices [1,2,3]. The electron sheet densities of 1013 cm−2 were found to be obtained by using AlGaN barriers when the Al content is typically 20–25% [3]. The large reverse leakage current occurring in AlGaN/GaN HEMTs increase the noise at low-frequency and leads to current collapse, limiting the applicability of such devices [4]. The leakage current flowing through the extended defects such as threading dislocations (TDs) are inevitably generated because of the large lattice mismatch and the different thermal expansion coefficients between (In,Al)GaN film and sapphire (or Si) substrate [5,6,7].
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