Intrinsic recombination radiation from GaP

Intrinsic recombination radiation has been detected in GaP crystals grown by vapour transport on GaAs and GaP substrates and in the form of needles, using 50 KeV electron beam excitation in the temperature range 25°K to 80°K. The three major components of the radiation are associated with the decay of free excitons with the emission of the transverse acoustic, longitudinal acoustic and transverse optic phonons which conserve momentum for transitions across the indirect energy gap. Structure has also been observed associated with the emission of two phonons, and for T > 77 >K a phonon absorption component can also be detected. In crystals grown on GaAs substrates, a no-phonon component has been observed with a threshold at the intrinsic exciton energy gap. This is thought to be associated with the presence of arsenic and there is a corresponding shift in the band gap to lower energy. close agreement is observed between the measured shapes of the emission components and those computed by the principle of detailed balance from the intrinsic edge absorption spectrum, when the broadening associated with the crystal imperfections and anomalous structure in the absorption spectrum are taken into account. The phonon energies derived from the emission spectra are in good agreement with the values determined from intrinsic edge absorption measurements.