Microscopic reverse-bias electroluminescence spectra and spectral images of 850 nm oxide-confined VCSELs during burn-in

Vertical-cavity surface-emitting lasers (VCSELs) are studied during high-current burn-in operation utilizing both reversebias electroluminescence (ReBEL) spectra and spectral images generated by means of a confocal scanning optical microscope equipped with a spectrometer. Recently unfiltered ReBEL images have proven to be sensitive to operation-induced changes of VCSELs because defect states having evolved during high-current stress trigger avalanche breakdown and give rise to ReBEL emission. Local current crowding during high current burn-in leads to spatial distributions of ReBEL emission being characteristic to the aging status and contain spectral portions due to quantum well as well as AlGaAs barrier emissions. In contrast, electroluminescence spectra measured under near flatband conditions exhibit only quantum well emission at 845 nm. ReBEL spectra show a dominating AlGaAs barrier emission at short wavelength and a weak long-wavelength quantum well emission being redshifted due to quantum-confined Stark effect under avalanche electric field.