Application of anodization in Oxygen plasma to fabrication of GaAs IGFET's

Anodic oxide grown in oxygen plasma has been used to fabricate the gate insulator of GaAs insulated-gate field-effect transistors (IGFET's), by patterning the gate electrode of 1.2 µm in length with the dry etching process. It is found that the oxidation process does not damage the electrical property of the channel layer. However, the trap states at the interface between the oxide and the channel affect the low-frequency characteristics, especially at positive gate voltage. The IGFET's show a good high-frequency performance comparable to GaAs MESFET's. The following characteristics are confirmed from the measurement of the S-parameters and the equivalent circuit analysis; the maximum stable power gain is 11.4 dB at 8 GHz, the cut-off frequency of the unilateral power gain is 48 GHz, and the intrinsic gain-bandwidth product is 18 GHz. The minimum noise figure is measured to be 4.8 dB at 8 GHz.