A new photoelectrochemical etching method for the fabrication of GaN MESFETs

A new photoelectrochemical etching method was developed and employed for th e fabrication of GaN metal-semiconductor field effect transistors (MESFETs) . The unique etching process utilizes a photoresistive mask and a KOH-based etchant. The etching rate of the etchant, with 1.0 mol% of KOH, for n-GaN is as high as 1600 Angstrom/min at a Hg-illumination intensity of 35 mW/cm( 2). The fabricated GaN MESFET exhibited a current saturation at V-ds = 10 V and a pinch-off at V-gs = -3 V. The peak drain current of the device was a bout 25 mA/mm at 300 K, and the value remained almost same for 500 K operat ion. The insensitivity of the device performance to temperature was attribu ted to the defect-related high activation energy of dopants for ionization and to the band-bending at the subgrain boundaries in GaN thin films.