Excitation Intensity and Temperature-Dependent Performance of InGaN/GaN Multiple Quantum Wells Photodetectors
Résumé
In this article, we investigate the behavior of InGaN-GaN Multiple Quantum Well (MQW) photodetectors under different excitation density (616 µW/cm 2 to 7.02 W/cm 2) and temperature conditions (from 25 • C to 65 • C), relating the experimental results to carrier recombination/escape dynamics. We analyzed the optical-to-electrical power conversion efficiency of the devices as a function of excitation intensity and temperature, demonstrating that: (a) at low excitation densities, there is a lowering in the optical-to-electrical conversion efficiency and in the short-circuit current with increasing temperature; (b) the same quantities increase with increasing temperature when using high excitation power. Moreover, (c) we observed an increase in the signal of photocurrent measurements at sub-bandgap excitation wavelengths with increasing temperature. The observed behavior is explained by considering the interplay between Shockley-Read-Hall (SRH) recombination and carrier escape. The first mechanism is relevant at low excitation densities and increases with temperature, thus lowering the efficiency; the latter is important at high excitation densities, when the effective barrier height is reduced. We developed a model for reproducing the variation of J SC with temperature; through this model, we calculated the effective barrier height for carrier escape, and demonstrated a lowering of this barrier with increasing temperature, that can explain the increase in short-circuit current at high excitation densities. In addition, we extracted the energy position of the defects responsible for SRH recombination, which are located 0.33 eV far from midgap.
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