Time-resolved mid-infrared photoluminescence spectroscopy of an undoped InAs substrate

Time-resolved mid-infrared photoluminescence (PL) spectroscopy of an undoped InAs substrate has been achieved with wavelength upconversion and time-correlated single photon counting methods. The substrate exhibits multiple PL peaks at photon energies of around 0.415 eV, and the peak positions and intensities change as the temperature is varied from 3.7 to 80 K. The dominant PL peaks are attributed to free and donor-bound excitons and radiative recombination between electrons at the Fermi edge in the conduction band and holes in the valence band edge. The PL lifetime of the excitons is 12 ns, which is four times longer than that of GaAs. The band edge electron–hole recombination has a longer PL lifetime of 60 ns at 20 K. The unveiling of luminescence dynamics in narrow bandgap semiconductors will contribute to the development of mid-infrared light-emitting devices.