Nonradiative Relaxation Processes of Excitons inβ-ZnP2Studied by Photocalorimetric Spectroscopy

Abstract

Nonradiative relaxation processes of excitons have been investigated by means of photocalorimetric (PC) spectroscopy in the exciton resonance region of β-ZnP 2 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 1 s longitudinal exciton energy E L to the band gap energy E g . The heat generation, however, is largely suppressed in the 1 s 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 t...