Strain and composition engineering of excited-state carrier recombination dynamics in GaAs/GaP and GaAs/AlAs superlattices: insights from time-domain nonadiabatic molecular dynamics simulations

Abstract

The performance of a semiconductor device is critically determined by microscopic excited-state carrier dynamics (ESCD), and tuning ESCD enables specific optoelectronic functions. In the realm of semiconductor devices, III–V-semiconductor-based superlattices (III–V-SLs) are particularly noteworthy. Given the limited understanding of ESCD modulation in III–V-SLs, this study systematically explores how strain and composition engineering affect the ESCD of GaAs/GaP and GaAs/AlAs superlattices using time-domain nonadiabatic molecular dynamics simulations at 300 K. GaAs/GaP and GaAs/AlAs exhibit carrier lifetimes of 11 and 5 ns, respectively. Strain from −3.0% to 3.0% shortens the carrier lifetime by four orders of magnitude in GaAs/GaP and GaAs/AlAs, enabling applications ranging from photovoltaics requiring long carrier lifetimes to photodetectors and light-emitting diodes, which benefit from moderate and short lifetimes. Carrier-lifetime evolution under strain is dominated by nonadiabatic couplings (NAC), with the band gap exerting the strongest influence on NAC. In GaAs/GaAs_xP_1−x and GaAs/Ga_xAl_1−xAs, band gap, electron–phonon coupling, nuclear velocity, and wave function overlap collectively influence the composition-dependent NAC evolution. Notably, carrier dynamics in GaAs/GaP is more sensitive to strain and composition than in GaAs/AlAs. These findings provide valuable insights into the ESCD of III–V-SLs, supporting the design and synthesis of high-performance optoelectronic and photovoltaic devices.