Scanning electron and laser beams induced current (SELBIC) method for observing failures in GaAs high electron mobility transistors

The electrical imaging observation of failures in GaAs high electron mobility transistors (HEMTs) is performed using scanning electron and laser beams induced current (SELBIC) method. An electron beam and infrared (IR) laser beam with a wavelength of 1064 nm irradiate coaxially from each side of a HEMT sample. When HEMT sample#1 and #2 are scanned from the back surface using a laser beam, a high contrast spot in the current image of sample#1 was observed between the gate and source regions. Since the II–VV characteristic between the gate and source shows an increase in leakage current, the high contrast spot in the current image is suggested to be an electrically active failure. The current image is compared with the image under electron beam irradiation. It is ascertained by a cross sectioning technique with focused ion beam (FIB). The current spot is due to a crack causing a local short circuit in an insulating layer.