Demonstration of Millimeter-Wave GaN IMPATT Oscillator at Ka-band

An experimental demonstration of a GaN IMPATT oscillator operated at Ka-band is being reported for the first time. The GaN IMPATT diode adopted a single-drift-region p
⁺
-n structure grown on native GaN substrates. A beveled mesa etch with SiO
2
sidewall passivation enabled robust avalanche breakdown and high current capability in the diodes. Up to 16.5 kA/cm
²
was measured under pulsed operation when the bias exceeded avalanche voltage. To minimize the series resistance, the substrate was first thinned down to 100 μm and then further down to 20 μm in thickness. The avalanche was preserved in the diodes after the entire process of substrate thinning, dicing, and packaging. RF oscillation characterization was performed in pulsed mode in a microstrip cavity circuit. An oscillation up to 38.0 GHz was achieved at a biasing current density of 10.2 kA/cm
²
. The peak output power generated by the device was 7 dBm at this frequency. The oscillation frequency could be tuned from 28.8 to 38.0 GHz by varying the biasing current.