Abstract
We report the first demonstration of operational InGaN-based thin-film transistors (TFTs) on glass substrates. The key to our success was coating the glass substrate with a thin amorphous layer of HfO2, which enabled a highly c-axis-oriented growth of InGaN films using pulsed sputtering deposition. The electrical characteristics of the thin films were controlled easily by varying their In content. The optimized InGaN-TFTs exhibited a high on/off ratio of ~108, a field-effect mobility of ~22 cm2 V−1 s−1, and a maximum current density of ~30 mA/mm. These results lay the foundation for developing high-performance electronic devices on glass substrates using group III nitride semiconductors.
Highlights
Coating glass substrates with HfO2 is important for obtaining InGaN films with smooth surfaces and for suppressing electron scattering caused by rough interfaces between channel and gate dielectrics
Source and drain electrodes (Ti/Al: 10 nm/30 nm) were subsequently deposited by sputtering, and a-HfO2 gate dielectrics were deposited on the InGaN films by atomic layer deposition (ALD) at 200 °C
We found that highly c-axis-oriented InGaN films can be grown by pulsed sputtering deposition (PSD) on glass coated with amorphous HfO2 layers
Summary
InGaN films were grown by PSD15,16,20,21 and their In content was modulated by changing the supply ratio of In and Ga. Before the growth, fused silica glass substrates were degreased by ultrasonic cleaning in ethanol for 5 min. InGaN films were grown on the glass substrates, with and without an amorphous HfO2 layer deposited by ALD at 200 °C. Tetrakis(dimethylamido)hafnium (Hf(NMe2)4) and O3 were used as precursors for the amorphous HfO2. The growth of InGaN was carried out at 300 °C. Metal droplets remaining on the surface of the InGaN films were immediately removed using HCl (~35%) solution. The InGaN samples were cut into specimens with a size of 10 mm × 10 mm and subjected to the XRD measurements
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