Spectral characteristics of InGaAsP/InP infrared emitting diodes grown by LPE

InGaAsP/InP double heterostructure infrared emitting diodes were grown by liquid phase epitaxy. Eleven different diodes were fabricated with optimal spacing of their peak emission wavelengths in order to have sufficient overlapping of their spectra. The spectral characteristics of these different wavelength InGaAsP/InP infrared emitting diodes were studied systematically. The spectral bandwidth of the LEDs was usually broader than theoretically predicted. The broadening of the emission spectra of the LEDs on the long wavelength side can be associated with nonuniform active layer composition. Investigation of the cross-section of the LED structures showed that their active layer had a thin layer at the InP interface with shifted composition. The band gap difference between the bulk and the transition layer was found to be in correlation with the long wavelength side broadening of the emission spectra of the corresponding LEDs.