Growth mechanism and electronic properties of stacking mismatch boundaries in wurtzite III-nitride material

Abstract

III-nitride materials including AlN, GaN, and InN are promising for semiconductor industry applications; however, the material growth process gives rise to high defect densities in the epilayer, which can affect the device performance. A systemical understanding of the defect physics is necessary for realistic applications. Among the defects in III-nitride materials, the stacking mismatch boundary (SMB) is a kind of extended defect generated due to the presence of a stacking fault, whose structure-function relationship is still not well understood. Here, we report on a first-principles investigation of the growth and electronic properties of the SMB in III-nitride materials. Based on the wurtzite crystal symmetry, it is found that the SMBs can be categorized into three basic types, depending on the terrace edge of the coalescent normal and stacking-fault regions on the (0001) surface, and the corresponding edge type is controllable by varying the chemical potential and initial nucleation size during the material growth process. Additionally, it is revealed that SMBs produce in-gap states in III-nitride materials with various properties, including itinerant magnetism with high Curie temperature and optical transition correlated with the experimentally observed sub-band-gap spectrum. It is worth noting that one type of SMB is a possible source of the yellow luminescence that is widely observed in GaN. Our findings add comprehensive insight into the SMB in III-nitride materials; the unique growth controllable property of an SMB is also a possible routine to broaden the applications of III-nitride materials.