Experimental Study of Barium Strontium Titanate High-K Gate Dielectric on Beta Gallium Oxide Semiconductor

Date of Award


Degree Name

M.S. in Electrical and Computer Engineering


Department of Electrical and Computer Engineering


Guru Subramanyam


Development of high permittivity, or high-κ dielectrics for ultra-wide bandgap (UWBG) materials, such as β-Ga₂O₃, is critical to the electric field management in devices made with UWBG semiconductor materials [1]. Typically, high-κ dielectrics are deposited using high-temperature processes, such as pulsed laser deposition (PLD), which poses a significant challenge in the development of β-Ga₂O₃ devices. This thesis is focused on studying the quality of high-κ dielectric BaₓSr₁₋ₓTiO₃ (BST) deposited using PLD on ALD-grown SiO₂ on Sn-doped (010) β-Ga₂O₃ substrates. The PLD deposition parameters of thickness, target composition, and deposition temperature were varied to study multiple variations of BaₓSr₁₋ₓTiO₃ MOSCAP devices. BST deposition conditions were identified to produce a device with an effective breakdown field Eeff,BD ≥ 30 MV/cm within the BST/SiO₂ dielectric stack with a current leakage ≤ 10⁻⁸ A/cm² at Eeff< 5.8-7.6 MV/cm. Interface defect density was analyzed for these devices using the conductance method [2] and photo-assisted capacitance-voltage (C-V) measurements [3]. The devices with the largest Eeff,BD showed a shallow-level defect density Dit ≤ 10¹² cm⁻²-eV⁻¹ and deep-level defect density Nit ~ 2x10¹² cm⁻². The extracted shallow and deep-level interface defect densities indicated a high defect density at the dielectric/semiconductor interface, affirming the need for further interface optimization. This work demonstrates successful fabrication of a BST on β-Ga₂O₃ MOSCAP device, offering supporting motivation for further investigation into the use of high-κ BST for β-Ga₂O₃ devices.


Electrical Engineering, Engineering, Materials Science, Nanotechnology, dielectrics, gallium oxide, MOSCAPs, characterization, BST, Barium Strontium Titanate

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