A 2.4 GHz-Band Amplifier with β-Ga ₂ O ₃ MESFET Fabricated by Mist CVD Method

Thin films of β-Ga<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>, one of the ultra-wide bandgap power semiconductors of β-Ga<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>, which are attracting attention as the next-generation devices, were epitaxially grown on β-Ga<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> substrates using the cost-effective mist chemical vapor deposition (CVD) method. A MESFET with a gate length of 0.45 μm and a gate width of 200 μm was fabricated on the substrate. To match the high impedance of the input and output, an amplifier circuit was constructed with a matching circuit connected directly to the high-frequency probe. A gain of 6.5 dB, a saturated output power of 12 dBm, and an added efficiency of 10% were obtained in the 2.4 GHz band. These results suggest that the mist CVD method can potentially be used for epitaxial growth in high-frequency devices at low cost.