Nonradiative Relaxation Processes of Excitons in [beta]-ZnP2Studied by Photocalorimetric Spectroscopy

• Published in: Journal of the Physical Society of Japan 2000-11, Vol.69 (11), p.3715
• Main Authors: Arimoto, Osamu, Umemoto, Shigeo, Nakamura, Kaizo
• Format: Article
• Language: English
• ISSN: 0031-9015; 1347-4073

Nonradiative relaxation processes of excitons have been investigated by means of photocalorimetric (PC) spectroscopy in the exciton resonance region of β-ZnP2 by detecting temperature increase of the crystal under excitation with a Ti:sapphire laser at 4.5 K. For singlet excitons, power of the light absorbed by the crystal is converted to that of the thermal heating of the crystal almost at a constant rate as high as about 80% in the energy range from the 1s longitudinal exciton energy EL to the band gap energy Eg. The heat generation, however, is largely suppressed in the 1s reflection band, where the exciton luminescence is also decreased in intensity, which suggests the presence of other optical process in this region such as resonant Rayleigh scattering. From comparison of the PC spectrum with excitation spectrum for the singlet exciton luminescence, it is found that a ratio of the PC signal to the luminescence intensity increases at the exciton resonances n=1, 2, 3 and 4. This fact indicates that the rate of the nonradiative decay of excitons relative to the emission of the luminescence is high at the exciton resonances. The PC spectrum for triplet excitons is also presented.