Interplay of carriers and deep-level recombination centers of 275-nm light-emitting diodes — Analysis on the parasitic peaks over wide ranges of temperature and injection density

Temperature-Dependent Carrier Recombination and Efficiency Droop of AlGaN Deep Ultraviolet Light-Emitting Diodes

“…Experimental results have revealed that multiple sources, e.g., extend dislocations, quantum confined Stark effect (QCSE), carrier delocalization, Auger recombination, and carrier leakage, lead to the lower EQE and severer efficiency droop in AlGaN-based DUV LEDs than those in InGaN-based visible LEDs [10], [12]- [14]. In AlGaN-based DUV LEDs, the aluminum-rich EBL tends to prevent holes from entering MQWs, leading to a poor hole-injection efficiency [12], whereas the high-energy carriers are inclined to drift out of high-defect-density MQWs due to the insufficient restriction [15]. Although having been frequently used to comprehensively investigate the mentioned issues, the ABC model takes only into account the recombination inside MQWs [16], namely Shockley-Read-Hall (SRH) non-radiative recombination, radiative recombination, and Auger recombination.…”

“…Thus, a modified ABC + f(n) model, where f(n) is associated with the carrier leakage, proves a better precision than the conventional one when fits to the experimental data [17]. Due to the widely reported leakage in AlGaN-based DUV LEDs [15], [18], it is reasonable to introduce the leakage term f(n) for a more detailed evaluation on the effect of carrier transfer and recombination.…”

Investigate the Double Peaks in Main Emission of UVB LEDs

“…Sample A provided the exciton emission at temperatures of up to 363 K. Several reports have described parasitic peaks extending from the low-energy side of the main peak for UVC LEDs. [22] These parasitic peaks are presumably associated with recombination occurring through deep level defects and electron over ow and through polarization doping recombination in the p-AlGaN neutral region. In this present study, we did not observe any obvious parasitic peaks from sample B at any temperature up to 363 K. Therefore, we suggest that defect-related recombination did not occur in sample B under the injection conditions in the temperature range from approximately 298 to 363 K. Accordingly, using the two-fold p-Al 0.55 GaN/p-Al 0.4 GaN structure (to improve the crystal quality), the 50-nm-thick p-AlGaN-to-p-GaN grading composition layer, and the 20-nm-thick p-GaN layer (to ensure a su cient number of holes and good ohmic contact) effectively depressed the emission band arising from defects or impurities.…”

Perspectives on UVC LED: Its Progress and Application

“…T peaks are believed to originate from two regions as radiation recombinati located in the quantum well, and the other in the p-type layer. They emit l high excitation densities, respectively, and thus, parasitic peaks that appe wavelength region can originate from different regions and different type tice defects [73]. The study of these parasitic peaks can determine the qua taxial layer of a device from one side and elucidate the mechanism of ca which provides a reference for the improvement of device epitaxy in the f tion, this group conducted research on the point-defect recombination in Shockley-Read-Hall recombination, trap-assisted recombination), leakage recombination, and other factors that affect the quantum efficiency [74] hand, Kneissl et al inferred that efficiency droop in AlGaN quantum-we tures are caused by an internal carrier loss process, analogous to what occu system.…”

“…These parasitic peaks are believed to originate from two regions as radiation recombination defects: one located in the quantum well, and the other in the p-type layer. They emit light at low and high excitation densities, respectively, and thus, parasitic peaks that appear in the same wavelength region can originate from different regions and different types of crystal lattice defects [73]. The study of these parasitic peaks can determine the quality of the epitaxial layer of a device from one side and elucidate the mechanism of carrier transport, which provides a reference for the improvement of device epitaxy in the future.…”