Determination of intervalley scattering rates in GaAs by subpicosecond luminescence spectroscopy

Subpicosecond Raman Study of Hot Electrons and Hot Phonons in GaAs

“…Both the electron and LO phonon temperatures predicted by this model are far too high compared with the observed temperatures. We note that our Te are comparable to those observed by Shah et al 2 using subpicosecond time-resolved photoluminesce~ce.…”

“…2 Thus at times shorter than 1 ps intervalley scattering can account for the very fast cooling of the hot r valley electrons we observed.…”

“…Optical techniques based on picosecond (ps) and femtosecond (fs) lasers have played an important role in these studies. 1 -4 In particular optical techniques such as tirr.e-resolved photo-induced absorption 1 • 3 and luminescence 2 have been used to study the relaxation and cooling of the hot electrons. The di~advantages of these optical techniques are that they do not provide info~reation on the phonons which are excited by the cooling electrons.…”

Free-carrier relaxation and lattice heating in photoexcited bismuth

“…In photoexcited semiconductors, carrier relaxation occurs in a series of stages 8 : 1. momentum relaxation within a valley is dominated by electron-acousticphonon scattering in non-polar semiconductors 9,10 and by electron-LO-phonon scattering in polar semiconductors 11 but electron-electron scattering becomes much more competitive [12][13][14] than in metals (and in some twodimensional systems, carrier-carrier scattering may dominate 15 ). Compared to a metal, the difference in timescale between electron-phonon and electron-electron scattering is substantially reduced, because (a) the density of final states in the electron-phonon scattering process is substantially less than in a metal, thus reducing the electron-phonon scattering rate 8,16 and (b) screening of the Coulomb interaction is much less effective in the low-density semiconductor plasma than in a metal, so that carrier-carrier scattering at small momentum transfer (i.e.…”

“…3. Carrier energy relaxation within each valley is dominated by carrier-carrier scattering, although LO and intravalley phonons may also play a substantial role 8,11,12 . Because of the large Coulomb interaction for small momentum transfer 13 , carriers relax their energy primarily within each valley or by exchanging heat between the carriers in different valleys.…”