Optical gain spectra of InGaAsP/InP double heterostructures

We report the first optical gain measurements on InGaAsP/ InP double heterostructures with composition corresponding to an emission wavelength of about 1.3 μm at 300 K. At optical pumping levels of about 1 MW/cm
²
the maximum gain values of the best samples available are 800 cm
^-1
at 2 K, 500 cm
^-1
at 77 K, and 200 cm
^-1
at 300 K. We conclude from low-intensity luminescence and absorption spectra, that the laser transition corresponds to free-carrier recombination between band-tail states, which are present even in not intentionally doped material. Although these tail states result in rather broad low-intensity luminescence, narrow gain spectra comparable to those of GaAs/GaAlAs double heterostructures are obtained.