Electrical characterization of high-k ( k > 115) crystalline SrTiO3 (STO) thin film integration with GaN with nanomembrane transfer process

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Abstract High-permittivity ( k > 115), crystalline SrTiO 3 (STO) thin films were transferred on GaN using a nanomembrane transfer technique for potential applications in high-voltage power devices, including transistors and diodes. The electrical properties of the transferred STO films were systematically characterized using MOS capacitors (MOSCAP), including leakage current characteristics, capacitance–voltage ( C – V ) behavior, dielectric constant, and frequency dispersion. The STO nanomembranes exhibited negligible leakage current, below the noise floor of the measurement system, up to bias voltages of 6 V and 11 V for the 50 nm and 200 nm thick membranes, respectively. The C – V characteristics indicated high dielectric quality, with minimal frequency dispersion observed over the frequency range of 10 kHz–500 kHz. The extracted dielectric constant (median) ranged from 50 to 110 for the 50 nm STO membrane and from 130 to 190 for the 200 nm STO membrane. Post-transfer thermal annealing in ambient atmosphere at 250 °C for two hours resulted in a modest enhancement of the dielectric constant by approximately 8%–20%. However, this improvement was accompanied by degradation in leakage current performance, manifested as a reduction of approximately 1–3 V in the bias range where leakage current was negligible. The underlying physical mechanisms contributing to these trends were analyzed and discussed. In addition, the statistical distribution of the extracted dielectric constant across different pad sizes and nanomembrane thicknesses was reported, and the possible contributors to the apparent trends were discussed.

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