Interactive study of electroreflectance and photocurrent spectra in InGaN/GaN-based blue LEDs

Abstract

We experimentally and theoretically investigate the relationship between the electroreflectance (ER) and photocurrent (PC) spectra, and how they can be utilized to estimate the flat-band voltage and the bandgap energy of the InGaN/GaN-based quantum-well (QW) structure in blue lighte-mitting diodes. With theoretical modeling of ER and PC spectra, we calculate the changes in both the refractive index (Delta n) and optical absorption (Delta alpha) spectra from experimental ER and PC data by using the Kramers-Kronig relation. Then, we compare Delta n (or Delta alpha) spectra obtained differently from the ER and PC data and try to comprehend their physical meanings interactively. From these combined studies, we propose an exact method of determining the flat-band voltage, the piezoelectric field, the emission energy, the effective bandgap energy, and the Stokes shift of a QW structure under the quantum-confined Stark effect (QCSE).