Nonradiative relaxation processes of excitons in beta-ZnP2 studied by photocalorimetric spectroscopy

Arimoto, O Uemoto, S Nakamura, K

O. Arimoto et al., Nonradiative relaxation processes of excitons in beta-ZnP2 studied by photocalorimetric spectroscopy, J PHYS JPN, 69(11), 2000, pp. 3715-3719

28

INGLESE

Article

Physics

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN

0031-9015 → ACNP

69

11

2000

3715 - 3719

ISI

0031-9015(200011)69:11<3715:NRPOEI>2.0.ZU;2-P

Nonradiative relaxation processes of excitons have been investigated by mea ns of photocalorimetric (PC) spectroscopy in the exciton resonance region o f beta -ZnP2 by detecting temperature increase of the crystal under excitat ion with a Ti:sapphire laser at 4.5 K. For singlet excitons, power of the l ight 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 r ange from the Is longitudinal exciton energy E-L to the band gap energy E-g . The heat generation, however, is largely suppressed in the Is reflection band; where the exciton luminescence is also decreased in intensity, which suggests the presence of other optical process in this region such as reson ant 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 reson ances n = 1, 2, 3 and 4. This fact indicates that the rate of the nonradiat ive decay of excitons relative to the emission of the luminescence is high at the exciton resonances. The PC spectrum for triplet excitons is also pre sented.