ABSTRACT
Piezoelectric and spontaneous polarization effects are two of the most interesting parameters in GaN based research. Locally strain generated fields in conjunction with threading dislocations can create piezoelectric induced sheet charge density and electric fields at a free surface or a heterostructure interface near the dislocation. An additional important structural property of group III nitrides with wurtzite structure, which strongly affects the orientation of the spontaneous and piezoelectric polarization, is the polarity of the crystals. The polarization effect improves device performance and induces in many device applications; like it increases barrier height, reduces gate leakage current, enhances current handling capability. This misfit strain as discussed in the following section causes the piezoelectric polarization.
