Photoluminescence characterization of Nd-doped GaP grown by metalorganic chemical vapor deposition

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Abstract
Nd‐doped GaP is grown by metalorganic chemical vapor deposition and characterized by photoluminescence measurements. The liquid‐helium‐temperature luminescence spectra due to Nd intra‐4f‐shell transitions depend on the growth conditions of the crystals. Some crystals show only a small number of luminescence lines, while some other crystals show many luminescence lines, indicating the presence of many kinds of Nd light emitting centers. Intensities of some luminescence lines begin to decrease at about 50 K and they are below the detection limit at 100 K. However, thermal quenching of some other luminescence lines begins at higher temperatures and their luminescence can be observed up to room temperature. A study on photoexcitation with above‐ and below‐band gap energy photons reveals that some Nd centers can be excited even by below‐band gap energy photons, indicating the role of mid‐gap levels, in the excitation mechanism, related to the Nd centers. A further comparative study of luminescence characteristics on GaP and GaAs doped with Nd shows that the experimental evidence is consistent with the excitation mechanism proposed for intra‐4f‐shell luminescence of Yb in InP, where the rare earth 4f shells are excited by way of electron‐hole recombination at rare‐earth‐related trap levels with successive energy transfer.