Abstract
The effects of rapid thermal annealing (RTA) on Schottky barrier diodes (SBDs) made from oxygenated aluminum nitride (AlN) thin films deposited on a silicon carbide (SiC) substrate using radio frequency sputtering were investigated. The annealed SBD devices exhibited a 10x increase in the on/off current ratio vs. non-annealed devices for measurement temperatures ranging from 300 K to 450 K. The ideality factor, derived from the current density–voltage (J-V) characterization, increased by a factor of ~2.2 after annealing, whereas the barrier height decreased from ~0.91 to ~0.68 eV. Additionally, Auger electron spectroscopy indicated decreased concentrations of atomic oxygen in the AlN thin film, from ~36% before, to ~24% after annealing. This may have contributed to the reduced barrier height and improved on/off ratio in the annealed AlN/SiC diodes.
Highlights
Owing to its high bandgap (~6.2 eV), high breakdown voltage, high thermal conductivity and low thermal expansion, aluminum nitride (AlN) is of considerable interest for the manufacture of deep ultraviolet (DUV) lasers, LEDs and detectors [1,2]
The J-V characteristics on a log scale are shown in oxygenated-AlN SBDs measured at 300 K
It has been reported treatment of AlN/silicon carbide (SiC) structures may be important for modifying the behavior of devices by that, as a result of annealing in a nitrogen atmosphere, the atoms in the film layer may acquire enough controlling the barrier height and on/off ratio
Summary
Owing to its high bandgap (~6.2 eV), high breakdown voltage, high thermal conductivity and low thermal expansion, aluminum nitride (AlN) is of considerable interest for the manufacture of deep ultraviolet (DUV) lasers, LEDs and detectors [1,2]. SiC a suitable substrate on which to grow AlN thin films. AlN grown at high temperature on sapphire substrates need to be relatively thick (upwards of ~600 nm) for achieving high-quality films [6], limiting its suitability for certain device types. Sputtered thin films are known to have the disadvantage of possible degradation during deposition due to the plasma. This can be avoided by using molecular beam epitaxy (MBE), which allows highly controlled thin film growth. As the deposition of AlN thin films at low temperatures has become increasingly important, the sputtering technique is promising under circumstances where low-temperature deposition, large-scale or conformal film growth are to be readily achieved [7,8,9,10]
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