  We report on the demonstration and investigation of Ta2O5 as high-\k{appa}
dielectric for InAlN/GaN-MOS HEMT-on-Si. Ta2O5 of thickness 24 nm and
dielectric constant ~ 30 was sputter deposited on InAlN/GaN HEMT and was
investigated for different post deposition anneal conditions (PDA). The gate
leakage was 16nA/mm at -15 V which was ~ 5 orders of magnitude lower compared
to reference HEMT. The 2-dimensional electron gas (2DEG) density was found to
vary with annealing temperature suggesting the presence of net charge at the
Ta2O5/InAlN interface. Dispersion in the capacitance-voltage (C-V)
characteristics was used to estimate the frequency-dependent interface charge
while energy band diagrams under flat band conditions were investigated to
estimate fixed charge. The optimum anneal condition was found to be 500{\deg} C
which has resulted into a flat band voltage spread (VFB) of 0.4 V and interface
fix charge (Qf) of 3.98x10^13 cm-2. XPS (X-ray photoelectron spectroscopy)
spectra of as deposited and annealed Ta2O5 film were analyzed for Ta and O
compositions in the film. The sample annealed at 500{\deg} C has shown Ta:O
ratio of 0.41.XRD (X-ray diffraction) analysis was done to check the evolution
of poly-crystallization of the Ta2O5 film at higher annealing temperatures.
