Characterization of dislocations and surface potential in III-V nitride heterostructures

The characterization of III-V nitrides by Electrostatic Force Microscopy (EFM) and Atomic Force Microscopy (AFM) is reported. The samples studied consist of Aluminum Gallium Nitride/Gallium Nitride (Al/sub x/Ga/sub 1-x/N/GaN) heterostructures grown by Metal Organic Chemical Vapor Deposition (MOCVD) on sapphire substrate. The Al concentration and the thickness of the top layer of the heterostructure (Al/sub x/Ga/sub 1-x/N) have been varied in this study. The morphology of the surfaces was determined by AFM, while EFM performed in conjunction with AFM was used to measure the surface barrier potential. The surfaces of these heterostructures show regular step flow growth pinned by dislocations (present in concentrations of 10/sup 8/-10/sup 9/ cm/sup -2/). The surface potential variation around the dislocations have been observed to be of 0.1-0.3 V and having a FWHM (as determined by EFM) of 100-200 nm.