Measurement of the Piezoelectric Field in InGaN/AlGaN Multiple-Quantum-Well Near-Ultraviolet Light-Emitting Diodes by Electroreflectance Spectroscopy

The piezoelectric field in InGaN/AlGaN-based multiple-quantum-well (MQW) near-ultraviolet light-emitting diodes (LEDs) was measured by electroreflectance and photocurrent spectroscopies. At forward and reverse biases, both electroreflectance and photocurrent spectra were studied by utilizing similar-structure samples with indium contents of ~4.5%, ~5.5%, ~6.5%, and ~7.5%. The influence of MQW and superlattice structures on the electroreflectance spectra was interactively identified. The relation between the defects and the diffusion of Mg acceptors through the defects into the MQWs was also observed and systematically confirmed through the capacitance-voltage characteristics. The effects of diffused Mg acceptors on electroreflectance spectra, depletion width, and the piezoelectric field were found. The strain relaxation caused by the defects was also systematically investigated. The calculated piezoelectric fields of these samples were in good agreement with the theoretically calculated values.