Picosecond phonon dynamics and self-energy effects in highly photoexcited germanium

被引:9
作者
Ledgerwood, ML
vanDriel, HM
机构
[1] Department of Physics, University of Toronto, Toronto, M5S 1A7
来源
PHYSICAL REVIEW B | 1996年 / 54卷 / 07期
关键词
D O I
10.1103/PhysRevB.54.4926
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
Self-energies and population kinetics of optical phonons in strongly photo-excited intrinsic and p-type doped germanium have been studied using picosecond Raman scattering measurements at 295 K for induced carrier densities up to 2 x 10(20) cm(-3). Time-integrated and time-resolved measurements indicate that the nonequilibrium phonon occupation number increases sublinearly and its temporal peak shifts as the photoexcited carrier density is increased above 10(19) cm(-3). A theoretical model of coupled carrier and phonon dynamics indicates that this can be attributed to nonequilibrium phonon reabsorption by holes undergoing intra-heavy-hole valence-band transitions. The time-integrated measurements also reveal broadening and shifting of the Raman lines: for a photoexcited carrier density of 2 x 10(20) cm(-3), the line broadening indicates that the phonon lifetime is reduced from its quiescent value of 4 ps to similar to 0.5 ps and the phonon frequency is reduced by similar to 8 cm(-1). We present a microscopic model to describe the phonon self-energy effects that are caused by carrier-phonon interactions. The model indicates that the phonon broadening is consistent with primarily intra-heavy-hole valence-band transitions, while the phonon frequency renormalization is consistent with primarily inter-heavy-hole<->light-hole valence-band transitions.
引用
收藏
页码:4926 / 4935
页数:10
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