Evaluation of High-Temperature High-Frequency GaN-Based LC-Oscillator Components

In this work, an evaluation of the performance of discrete elements intended for an L-band high-temperature GaN-based LC-oscillator is carried out between room temperature and 300 °C. GaN high-electron mobility transistors (HEMTs) on sapphire substrate, metal- insulator-metal (MIM) capacitors, thin-film inductors, and resistors on sapphire and quartz substrates are fabricated and characterized through dc and S-parameter measurements up to 20 GHz. The GaN HEMTs on sapphire achieved ft of 18 GHz and fmax of 30 GHz at room temperature and ft of 11 GHz and fmax of 21 GHz at 300 °C while maintaining dc gate leakage below 0.1 mA/mm at 300 °C. MIM capacitors are characterized at temperatures up to 300 °C and at frequencies up to 10 MHz, showing stable capacitance values with changes as small as 1.37% over the entire temperature range. Planar spiral inductors are characterized using S-parameter measurements up to 20 GHz and 300 °C. While a temperature stable maximum oscillation frequency above 1 GHz is achieved, the quality factor degrades by up to 48% at 300 °C. A detailed analysis of the temperature dependence of the inductor is given.