Minimization of leakage current of recessed gate AlGaN/GaN HEMTs by optimizing the dry-etching process

The backward cur rent of Schottky contacts on unintentionally doped GaN samples prepared by different dry-etching methods was investigated. It was found that an ion beam etching (IBE) process with an accelerating voltage of 250 V under an angle of 20 degrees to minimize channeling achieves the best results. The backward current in this case is 4 x 10(-10) A/mu m(2) compared to the backward current of the unetched sample of I x 10(-7) A/mu m(2) at -100 V. With this process, recessed gate HEMTs on AlGaN/GaN heterostructures grown by low pressure MOVPE were fabricated and compared to HEMTs without recess. The applied gate recess etching technique improves the leakage current by nearly a factor of two. The maximum transconductance is improved from 40 mS/mm to 60 mS/mm at a gate length of 4 mu m.