Sub-Picosecond Luminescence Spectra of Photoexcited Electrons Relaxation in p-GaAs

Abstract

Femtosecond lasers have allowed closer examination of the dynamics of photoexcited carriers in semiconductors during the first tens of femtosecond after laser excitation^1–3. In particular, the ultrafast thermalization and relaxation of minority photoexcited carriers in p-GaAs have been a subject of intensive experimental investigations. For example, Furuta and Yoshii² used time resolved photoluminescence to examine minority electron relaxation over a wide range of acceptor concentrations and demonstrated the importance of electron-hole interaction in the relaxation of the photoexcited minority electrons at high acceptor concentrations. However, because the energy used in the photoexcitation excitation process (1.9 eV) generated electrons with energies above the intervalley transfer threshold, energy loss through intervalley phonon emission contributed to the overall energy and momentum relaxation process. More recently, Rodrigus and coworkers³ also examined the relaxation of photoexcited minority electrons in p-GaAs using shorter laser pulses with energies below the intervalley transfer process in order to minimize the role of intervalley phonons and examine the role of e-h in the cooling process. They also compared the measured electron temperatures with Monte Carlo simulations and obtained good agreement between the measured and simulated data.