Abstract

We report the first picosecond luminescence measurements of hot carrier cooling rates in the II-VI semiconductor CdSe. We find that the carrier energy loss rates reduce with the excitation density n_o. The rates are much smaller than those expected in a simple theory of carrier energy transfer to the lattice via various phonon emission processes. At n_o = 8 × 10¹⁷ cm⁻³ for example, the rates are reduced by as much as factor of 75. We present a detailed comparison with the theory including the effects of hot phonons and all relevant energy loss mechanisms. We find that a large, density dependent value of 6 to 9 ps for the optical phonon lifetime (at 8 K) is required to explain the results.

© 1994 Optical Society of America