Relaxation of piezoelectric fields near sidewalls of InGaN/GaN micro light-emitting diodes investigated by capacitance–voltage characteristics

The junction theory derived from the conventional p-n junction structure shows discrepancies when compared to the actual characteristics of InGaN/GaN-based p-i-n light-emitting diodes (LEDs). In particular, it does not account for the information related to the piezoelectric field present in the InGaN/GaN quantum wells (QWs), nor does it include the details of the intrinsic layer. Therefore, for accurate capacitance–voltage (C–V) characteristics analysis of InGaN/GaN-based LEDs, a new junction theory that fully reflects the features of such a structure is required. In this study, using the junction theory of InGaN/GaN-based p-i-n diodes, information on the piezoelectric field existing in InGaN/GaN QWs is extracted from the C–V characteristics of different-sized LEDs. We investigate the difference in the piezoelectric field between the sidewalls and the inner region of micro-LEDs and demonstrate both from the C–V analysis and the micro-Raman spectroscopy that the outer region near sidewalls are relaxed and has a smaller piezoelectric field, with the relaxation reaching up to ∼3 μm from the sidewall.