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 ${f}_{\text {t}}$ of 18 GHz and ${f}_{\text {max}}$ of 30 GHz at room temperature and ${f}_{\text {t}}$ of 11 GHz and ${f}_{\text {max}}$ 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.