DC characterization of laser-debonded GaN HEMTs

Department of Physics, Stuttgart University, Stuttgart, Germany Received 5 June 2006, revised 18 October 2006, accepted 18 October 2006 Published online 22 January 2007 PACS 72.70.+m, 81.05.Ea, 85.30.De, 85.30.Tv We report experimental investigation of laser-assisted debonding of GaN high electron mobility transis-tors (HEMTs) grown by metalorganic chemical vapor deposition (MOCVD) technique on sapphire sub-strates. The debonded HEMTs were transferred onto silicon substrate for better thermal dissipation during operation. Dc characterization indicated no degradation in the I–V characteristics as long as the optimized laser power was used in the debonding process. Transmission electron microscopy (TEM) of the AlGaN/GaN heterojunctions before and after the laser debonding process did not indicate any increase in the dislocation density at the heterointerface. We have also conducted detailed characterizations of the low-frequency noise properties to investigate the defect properties over the entire active area of the device. Experimental data on the voltage noise power spectra measured from the same device before and after laser debonding indicated no significant change in the magnitude of the flicker noise over a wide temperature range. The results of XRD measurements revealed that the FWHM values before and after debonding are basically the same and also suggested that both out-of-plane tensile and in-plane compres-sive stresses present were both removed after the laser processing. Our results clearly demonstrate that the laser-assisted debonding process did not result in the increase in the material defect density.