Abstract: Annealing experiments were carried out at 200~600℃ for 1min and 5min on many batches of AlGaN/GaN HEMTs on the sapphire, and the DC characteristics before annealing and after cooling were compared and analyzed. Also measured were the change of the characteristics of the ohmic contacts and the schottky contacts. It is found that the optimized annealing condition for improving the device characteristics is 500℃ annealing for 5min. Under this condition the maximum transconductance is raised by 8. 9%, the reverse leakage of schottky gate is reduced by two orders of magnitude, and the threshold voltage moves toward the positive direction. The elevation of the schottky barrier height after annealing causes the reduction of gate leakage and the more depletion of channel electrons, which also leads to the change of the saturation current and the threshold voltage. The surface morphology of the schottky contact is observed after annealing by SEM. No obvious change is found for 500℃-annealed samples, but bubbling appears for 600℃-annealed ones.

Key words: high eletron mobility transistors, leakage current, threshold voltage, contact resistance