Excitation Intensity and Temperature-Dependent Performance of InGaN/GaN Multiple Quantum Wells Photodetectors

Abstract

In this article, we investigate the behavior of InGaN–GaN Multiple Quantum Well (MQW) photodetectors under different excitation density (616 µW/cm2 to 7.02 W/cm2) 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 JSC 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.

Optimizing performance and energy consumption in GaN(n)/In x Ga 1- x N/GaN/AlGaN/GaN(p) light emitting diodes by quantum-well number and mole fraction

“…This means that at high current the number of emitted photons remains constant above a certain threshold. To overcome this problem, structures with multiple quantum wells are necessary, in congruence with earlier studies [76]. LEDs [28].…”

Influence of V-pits on the electro-optical properties of high-periodicity InGaN MQWs

“…Hence, in the case of thicker p-GaN layer samples, for which V-pits have a smaller influence on the characteristics due to the sufficient planarization [33], [34], the current flow below the main diode turn-on is more affected by other conduction processes, possibly trap-assisted tunneling phenomena [35] and other trap-mediated conduction processes [19]. In conclusion, the incomplete planarization of V-pits, particularly evident in the thinnest p-GaN layer sample, results in an overall lower sample quality [36], [37]. This results in an early turn-on voltage and different current-voltage characteristic with poor electrical performance especially at low to moderate current levels.…”

Degradation of GaN-based InGaN-GaN MQWs solar cells caused by thermally-activated diffusion

“…1.0×10 0 1.5×10 3 3.0×10 3 Figure 2 (a) reports the normalized short-circuit current measured during the constant power optical stress at 175 °C. At each step of the stress it is possible to observe an initial increase in the monitored current, due to device self-heating, which leads to an increase in thermionic emission of carriers photogenerated inside the quantum well 10 . This trend is more visible in the first two step of Figure 2 (a), where results are presented in linear horizontal scale, to describe the initial increase (the following steps after the axis break are plotted in logarithmic scale).…”