Static induction transistors optimized for high-voltage operation and high microwave power output

An optimized static induction transistor (SIT) design utilizing local oxidation in a self-aligned geometry is described. Devices with 10.5- and 7-µm pitch (gate-to-gate spacing), which have been optimized with respect to epitaxial layer thickness and resistivity, have attained a combination of operating frequency and breakdown voltage which is much higher than devices made with other technologies. The 10.5-µm pitch SIT´s have a blocking voltage of 170 V with 6-dB gain at 225 MHz and 10-dB gain at 900 MHz. Typical multicell power devices have demonstrated 110-W output power at 225 MHz with 65-percent drain efficiency and 25 W at 900 MHz with 40-percent drain efficiency, operated at voltages in excess of 100 V de bias. The 7-µm pitch SIT´s have a blocking voltage of 140 V and the same power gain performance at 225 and 900 MHz as the 10.5-µm pitch devices, but with higher effiency and a higher maximum frequency of operation. Typical multicell power devices of this type have achieve 110-W output power at 225 MHz with 70-percent drain efficiency and 25 W at 900 MHz with 55-percent drain efficiency operated at 90 V de bias.