Photoluminescence Characterization of Nonradiative Recombination Centers in Light Emitting Materials by Utilizing Below-Gap Excitation: A Mini Review of Two-Wavelength Excited Photoluminescence

Abstract

We have developed an optical method of detecting and characterizing nonradiative recombination (NRR) centers without electrical contact. The method combines a belowgap excitation (BGE) light with a conventional above-gap excitation light in photoluminescence (PL) measurement, and discriminates the PL intensity change due to switching on and off the BGE. A quantitative analysis of the detected NRR centers became possible by utilizing the saturating tendency of the PL intensity change with increasing the BGE density due to trap filling effect. Some experimental results of AlGaAs, InGaN, and AlGaN quantum wells were shown to allocate the development and present status as well as to exemplify their interpretations.Keywords: Internal quantum efficiency; photoluminescence; nonradiative recombination; below-gap excitation; defect states. INTRODUCTIONLight emitting diodes (LEDs) and laser diodes (LDs) in near infrared region realized fiber communication systems in 1970's [1] and provided an infrastructure of the world wide web of huge digital data link. The realization of blue and green LEDs through steady efforts on crystal growth technique of GaN [2-3] opened another revolution in lighting and display applications since three primary colors have been provided by efficient solid state light sources. Light-based science and technology are becoming more and more important for human society as vast information comes from our sense of sight.