DC and pulsed behaviour of undoped and doped AlGaN/GaN/SiC HEMTs before and after Si/sub 3/N/sub 4/ passivation

The comparison of undoped and doped devices fabricated on AIGaN/GaN heterostructure before and after passivation is investigated. The de and pulse behaviour is shown where an improvement of the drain saturation current of 22 % and 6 % in undoped and 5 xlO¹⁸ cm^-3 doped sample, respectively, after the surface passivation was measured. The recovery of the drain saturation current in 4 μs of the applied pulse increased from ~73 % to ~89 % after the passivation for both, undoped and doped devices. Also the output dc and pulse characteristics of unpassivated, undoped collapse-free HEMTs are presented.