Hot Carrier Cooling Study of ZnCdSe Epilayers

The hot carrier dynamics of ZnCdSe epilayers were studied using the femtosecond time-resolved photoluminescence up-conversion technique. The hot carriers release the excess energy primarily through scattering with longitudal optical phonons. The optical phonon emission times of the hot carriers were fitted from the carrier cooling curves and found to be 40 ps for both samples with different Cd concentrations. The initial temperature T_o was estimated below the theoretical calculation due to the fact that these hot carriers reach thermal equilibrium in a time scale faster than the experimental temporal resolution. The hot phonon effect is not prominent in the present work for the excitation density of 10¹⁷ cm^-3.