Piezoelectric polarization associated with dislocations in wurtzite GaN

Abstract

The piezoelectric polarization and its associated charge density are calculated for edge, screw, and mixed dislocations oriented parallel to the c axis in wurtzite GaN. It is shown that the polarization field generated by screw components of dislocations is divergence free, and thus does not generate electric fields. Edge dislocations produce polarization fields that have nonzero divergence only at interfaces. These characteristics minimize the electrical and optical effects of the dislocations mediated by the piezoelectric effect.

Local polarization switching in the presence of surface-charged defects: Microscopic mechanisms and piezoresponse force spectroscopy observations

“…͑A4͒ describes a continuous distribution resembling that of a charged dislocation line, in agreement with analysis in Ref. 53. The dimensionless overlap integral I S ͑r , l , x͒ in Eq.…”

“…53 In the limit ͉x 01 − r d ͉ ӷ d, the tip is well-separated from the defect, and hence, the defect role on tip-induced switching is minimal. Therefore, here we analyze the switching behavior for ͉x 01 − r d ͉ϳd.…”

Measurement of surface contact potential of AlGaN/GaN heterostructure and n‐GaN by Kelvin probe force microscopy

“…This is completely different from the observation of Koley et al [12], which reported that the variations in surface potential around the dislocations in AlGaN/GaN heterostructure was larger in diameter and smaller in magnitude than that in n-GaN. Calculation by Shi et al [24] has suggested that the surface charge densities due to piezoelectric polarization around dislocations in AlGaN/GaN heterostructure were the same order as that in n-GaN. Here, we suggest that the difference between the surface potential variations at dislocation in AlGaN/GaN heterostructure and that in n-GaN might be related to several possible factors.…”

Local electronic properties of AlGaN/GaN heterostructures probed by scanning capacitance microscopy

“…29,30 In addition, theoretical studies have indicated that local strain, and consequently polarization, fields in the vicinity of threading edge dislocations can give rise to substantial surface potential variations in GaN. 31 We have performed numerical simulations using the Davinci three-dimensional device simulation program (Avant! Corporation) to assess the influence of charged threading edge dislocation lines on SCM image contrast.…”