Heterogeneously Integrated Flexible GaN RF Power Amplifier on SiC/Parylene Substrate

The development of flexible radio frequency (RF) systems has increased the demand for high-power flexible gallium nitride (GaN) amplifiers. In this letter, a heterogeneous integration process utilizing a silicon carbide (SiC)/parylene heterogeneously integrated substrate is proposed for flexible RF GaN power amplifier (PA). In this fabrication process, the GaN PA is first designed on a SiC substrate with 100 μm thickness and then thinned down to ~5 μm after adhering to a temporary carrier. Subsequently, a 25 μm-thick parylene layer is deposited directly onto the SiC substrate via chemical vapor deposition (CVD), forming a SiC/parylene substrate. The proposed substrate can improve thermal dissipation compared to a pure parylene substrate while maintaining flexibility. Finally, a flexible GaN PA can be obtained by peeling it off from the temporary carrier. By utilizing the proposed process, a flexible GaN PA with state-of-the-art output power is demonstrated. The continuous-wave (CW) measurement results show that a saturation output power (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub>) of 28.3 dBm at 1.6 GHz under flat conditions is achieved for the flexible PA. And the corresponding power-added efficiency (PAE) reaches up to 38.3%. The flexible performance of the power amplifier is also characterized under bending condition with a curvature radius of 3 cm, which exhibits less than 0.1 dB degradation in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub>. The results of this letter will be useful for flexible wireless communication systems requiring either high data-rate or long-distance transmission.