Optimization of the active region of InGaN∕GaN 405 nm light emitting diodes using statistical design of experiments for determination of interaction effects

Abstract

Output performance of InGaN based violet light emitting diode structures emitting at 405 nm was optimized using the statistical design of experiments (DOE) approach. Two separate DOEs were utilized to optimize the active region. The variables studied included the gallium flow rate, indium flow rate, temperature, well and barrier growth times, NH3 flow rate, and the silicon doping of the barrier while holding all other parameters and layers constant. Photoluminescence (PL) measurements were analyzed for wavelength, intensity, and full width at half maximum (FWHM) for each sample in both DOEs while electroluminescence measurements were completed for the samples from the second DOE and analyzed based on optical output power. Statistically valid transfer functions were obtained for each response based on the variables investigated. An overall improvement of 7% in the intensity with a reduction of 20% in the FWHM of the 405 nm PL band was obtained based on the starting point of the first DOE, while an improvement of 80% in intensity of PL with a 64% improvement in optical output power was obtained in the second DOE. Results show several interactions between various variables and indicate the complexity of GaN based growth kinetics. The significant effects are explained based on simulation of the structures.