Diagnosis of trapping phenomena in GaN MESFETs

In this work we present results related to the current/voltage characteristics collapse in GaN MESFETs. Two different failure mechanisms were observed, one of them clearly consists in a positive threshold voltage shift. Traps responsible for the “current collapse” were also characterized by means of different measurement techniques. Phototransient experiments show the presence of a capture barrier of 0.1 eV while by a spectroscopic technique four photoionization energy levels were estimated. Finally, electroluminescence measurements show the presence of visible and UV light, suggesting the presence of a self-recovery mechanisms