Investigation of Ta2O5 as an Alternative High- Dielectric for InAlN/GaN MOS-HEMT on Si

• Published in: IEEE transactions on electron devices 2019-03, Vol.66 (3), p.1230-1235
• Main Authors: Kumar, Sandeep, Kumar, Himanshu, Vura, Sandeep, Pratiyush, Anamika Singh, Charan, Vanjari Sai, Dolmanan, Surani B., Tripathy, Sudhiranjan, Muralidharan, Rangarajan, Nath, Digbijoy N.
• Format: Article
• Language: English
• Subjects: 2-D electron gas (2-DEG); Annealing; capacitance–voltage (<italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">C –<italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">V ); Crystallization; Current leakage; Dielectrics; Electric potential; Electron gas; Electron mobility; Gates; Handheld computers; HEMTs; high-<italic xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">k; high-electron mobility transistor (HEMT); High-k dielectric materials; Investigations; Logic gates; Photoelectrons; Spectrum analysis; Tantalum; Tantalum oxides; Ta₂O; X-ray diffraction
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2019.2893288

We report on the demonstration and investigation of Ta 2 O 5 as high-k dielectric for InAlN/GaN-MOS high-electron mobility transistor (HEMT)-on-Si. Ta 2 O 5 of thickness 24 nm and dielectric constant ~30 was sputter deposited on InAlN/GaN HEMT and was investigated for different post deposition anneal (PDA) conditions. The gate leakage was 16 nA/mm at −15 V which was ~five orders of magnitude lower compared to reference HEMT. The 2-D electron gas (2-DEG) density was found to vary with annealing temperature suggesting the presence of net charge at the Ta 2 O 5 /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 °C which has resulted into a flat band voltage spread ( \Delta {V}_{\text {FB}} ) of 0.4 V and interface fix charge ( {Q} _{\text {f}} ) of {3.98} \times {10}^{{13}} cm ^{-2} . X-ray photoelectron spectroscopy spectra of as-deposited and annealed Ta 2 O 5 film were analyzed for Ta and O compositions in the film. The sample annealed at 500 °C has shown Ta:O ratio of 0.41. X-ray diffraction analysis was done to check the crystallization of amorphous Ta 2 O 5 film at higher annealing temperatures.