Time-resolved luminescence study of amorphous phosphorus: temperature and excitation energy dependences

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Abstract
The author presents the dependence of the excitonic 'LE' band (near 1.15 eV) and the distant pair 'He' luminescence band of red amorphous phosphorus as a function of temperature and excitation energy. The LE band decreases rapidly with increasing temperature. Excited by 6 ns laser pulses HE luminescence can even be observed at room temperature, while with slowly chopped light the decrease is much stronger with increasing temperature. The HE peak position increases with increasing laser energy between 1.2 and 1.95 eV, where it has a maximum, and then decreases again for larger laser energies. Around 1.95 eV the longest lifetimes occur and also the highest excitation quantum efficiency. The author concludes that luminescence centres with spectral properties are resonantly excited with light around the band gap (1.95 eV). Thus the results favour a model including more than one type of luminescence centre. Fatigue measurements show that metastable centres are created with a rate comparable but somewhat smaller than in a-Si.