Hot Phonon and Intervalley Effects on Ultrafast Carrier Relaxation in InGaAs Quantum Wells

Understanding the thermalization dynamics and minimizing energy loss processes in nanostructured materials are essential in realizing advanced concept photovoltaic devices such as hot carrier solar cells [1,2]. In the present work, we compare ensemble Monte Carlo (EMC) simulation of carrier dynamics in semiconductor multi-quantum well (MQW) structures with ultrafast optical studies. The EMC simulations include nonquilibrium hot phonon effects, intervalley scattering, carrier-carrier scattering and degeneracy effects, as well as the conventional scattering mechanisms in III-V materials, all within a multi-subband framework for MQW structures [3]. The electron-hole temperatures in InGaAs multi-quantum-well structure have been extracted from photoluminescence (PL) spectroscopy under 405 nm and 980 nm continuous wave (cw) optical excitation, where high carrier temperatures under cw photoexcitation conditions have been previously reported [4]. We compare the effects of including nonequilibrium phonon effects as well as the inclusion of intervalley scattering in the EMC simulations on the simulated carrier distribution functions in comparison with the PL studies, where the electron temperatures calculated with realistic LO phonon lifetimes show good agreement with the experimentally measured carrier temperatures. Further, EMC analysis shows that the hot-electron temperature is predominantly due to nonequilibrium LO phonons, with a significant fraction of carriers residing in the upper L-valleys, as has recently been reported [5,6].<br/><br/>[1] L. C. Hirst & N. J. Ekins-Daukes, Prog. Photovoltaics Res. Appl. <b>19</b>, 286–293 (2011).<br/>[2] Y. Rosenwaks et al., Phys. Rev. B <b>48</b>, 14675–14678 (1993).<br/>[3] R. Hathwar et al., J. Phys. D. Appl. Phys. <b>52</b>, 093001 (2019).<br/>[4] H. Esmaielpour et al., Nat. Energy <b>5</b>, 336–343 (2020).<br/>[5] V. R. Whiteside et al., Semicond. Sci. Technol. <b>34</b>, 094001 (2019).<br/>[6] D. K. Ferry, Appl. Phys. Rev. <b>8</b>, 1–27 (2021).