Fig. 1: Dislocation-type characterization in GaN epitaxy.
From: Dislocation-assisted electron and hole transport in GaN epitaxial layers
a Different epitaxial sequences and AFM images of samples: (b) with GaN and (c) with AlN nucleation layer. The large trapezoidal β-type pits are associated with screw dislocations (TSDs), while the small triangular α-type pits are originated from edge dislocations (TEDs). The samples are referred to as TSD-dominant and TED-dominant, respectively. d Dislocation induced leakage current in GaN: Topography and c-AFM images, the yellow dotted line outlines the edge of the β-pit; The leakage generated by TED α-type pits (blue circle marked) in c-AFM is below the noise level of 0.4 pA, while the leakage current distribution corresponding to open-core TSD at six surfaces of β-type etching pits is uneven, and the maximum of leakage is about 1.6 pA. e Electric potential distribution of TSDs in GaN: Topography and EFM with left and right scan images and (f) multi cutline profile of EFM; The EFM corresponding to the β-type pit is a light spot, with a potential well about 1 V higher than the surface potential.
