Influence of SiN/sub x/ passivation on the surface potential of GaInAs and AlInAs in HEMT layer structures

摘要

The surface Fermi level of Ga/sub 0.47/In/sub 0.53/As and Al/sub 0.48/In/sub 0.52/As is determined by Hall measurements on InP-based HEMT-type van der Pauw structures without and with downstream PECVD SiN/sub x/ surface passivation. The passivation increases the surface Fermi level towards the conduction band-edge for both semiconductors in particular for low deposition temperatures. While the increase is clearly noticeable on GaInAs it appears less marked on AlInAs. From the finding that the resulting enhancement of carrier density in the GaInAs cap layer does not lower the DC channel resistivity of SiN/sub x/ passivated HEMT devices conclusions can be drawn about the path of the current in the source and drain regions.