High peak-power LSA operation from epitaxial GaAs

Gallium solution epitaxy, using a steady-state, temperature-gradient technique has been successfully used to grow high-quality, 150-µM thick gallium arsenide layers with less than 5 percent variation in electron density. A laser-probe, photoconductivity method has been used to precisely measure the relative variations of electron density. Using these epitaxial layers with 1.5-2 ×10¹⁵cm^-3electron concentration, LSA oscillations at X- and Ku-bands have been measured with up to 400-watt peak power and with more than 10 percent efficiency. A small iris circuit with a stepped ridge waveguide impedance transformer has delivered fundamental LSA oscillations in the X- and Ku-bands. Operating bias levels of up to 20 times threshold were observed on some diodes. The importance of the substrate (and contact) layer conductivity at the interface with the active layer, as well as the skin depth of the active layer, for efficiency and in preventing avalanche breakdown is explained. Frequency tuning with bias voltage and temperature is shown and discussed.