Carrier Relaxation Times in InAs/AlAs Superlattices: Modulating by Layers, Temperature, and Carrier Concentrations

The InAs/AlAs superlattice structures hold significant potential for application in low-noise avalanche photodetectors. With their performance in practical applications linked to their fundamental physical property of carrier relaxation time, this paper investigates the carrier relaxation times of InAs/AlAs superlattices across various mono-layers, temperatures, and carrier concentrations. Our investigation indicates that relaxation times span several tens of picoseconds, confirming that high-quality interfaces do not significantly reduce relaxation times in the manner that defect states might. Moreover, our study demonstrates that adjustments of the superlattice period can effectively modulate both the bandgap and carrier relaxation times, potentially impacting avalanche photodiode’s performance by altering electron-phonon interaction pathways and the bandgap width. We established that lower temperatures contribute to an increase in the bandgap and a suppression of high-frequency optical phonon vibrations, thereby lengthening relaxation times. Additionally, our observations indicate that in InAs/AlAs superlattices, the relaxation time increases as the excitation power increases, owing to the phonon bottleneck effect. These insights into InAs/AlAs superlattices’s carrier dynamics highlight its promising applicability in enhancing avalanche photodetectors, and may contribute to the optimized design of superlattices for specific application scenarios.