Static and Dynamic Cooling Rate of Photocreated Plasmas in Semiconductors

Abstract

The cooling of optically created semiconductor plasmas has been intensely investigated over the past several years (see the References in Ref. 1).¹ The main result is that the cooling rate has generally been found to decrease with increasing carrier density. This means that the rate of optical phonon emission by carriers slows down at a high plasma density. This was attributed either to the screening of electron-phonon interaction² or to the heating of optical phonons. In the present work we discuss conditions when screening is not essential. The phonon emission reduction is related to the fact that in a certain wave vector interval Aq the phonons reach equilibrium with the carriers, so that further emission of such phonons occurs only to compensate for their anharmonic decay.