In-situ passivation of quaternary barrier InAlGaN/GaN HEMTs

The passivation effect of the SiN cap was demonstrated through Hall measurements. A significant increase of the sheet resistance after ohmic contacts realization was observed on the sample without SiN in-situ passivation and related to surface charges. This change was not observed on the HEMT structures with in-situ passivation, regardless the SiN layer thickness, showing that the SiN cap is an effective way to reduce the density of electronically active states at the interface between the III-N layers and the passivation. In addition, the structures show state of the art transport properties with 2DEG densities of 1.6×1013 cm−2 and electron mobilities as high as 1800 cm2 V−1 s−1.