Photoexcitation of a direct-gap semiconductor by pulsed pumping

A theoretical investigation is made of optical excitation of an intrinsic direct-gap semiconductor in two limiting cases of slow and fast electron-electron relaxation. The dependences of the density and average energy of hot electrons on the pump energy are found. An equation describing the behavior of the electron temperature under optical excitation conditions is derived allowing for electron-phonon collisions in the case of fast electron-electron relaxation. An analytic solution obtained for the interaction with piezoelectric phonons shows that there is an optimal duration of a photoexcitation pulse which ensures the maximum temperature of hot electrons.