Strain Compensation and Trade-Off Design Result in Exciton Emission at 306 nm from AlGaN LEDs at Temperatures up to 368 K

Abstract

In this study, we suppressed the parasitic emission caused by electron overflow found in typical ultraviolet B (UVB) and ultraviolet C (UVC) light-emitting diodes (LEDs). The modulation of the p-layer structure and aluminum composition as well as a trade-off in the structure to ensure strain compensation allowed us to increase the p-AlGaN doping efficiency and hole numbers in the p-neutral region. This approach led to greater matching of the electron and hole numbers in the UVB and UVC emission quantum wells. Our UVB LED (sample A) exhibited clear exciton emission, with its peak near 306 nm, and a band-to-band emission at 303 nm. The relative intensity of the exciton emission of sample A decreased as a result of the thermal energy effect of the temperature increase. Nevertheless, sample A displayed its exciton emission at temperatures of up to 368 K. In contrast, our corresponding UVC LED (sample B) only exhibited a Gaussian peak emission at a wavelength of approximately 272 nm.

Very Low-Efficiency Droop in 293 nm AlGaN-Based Light-Emitting Diodes Featuring a Subtly Designed p-Type Layer

“…The biggest challenge when fabricating AlGaN-based UVB LEDs is the low doping efficiency of the p-AlGaN layer at high Al contents. Thus, we have previously suggested that one of the main reasons for the J-droop in AlGaN-based UVB LEDs is the insufficient conductivity of the neutral region of the p-AlGaN layers, with the number of holes injected into the MQWs resulting in a mismatch of the quasi-charge-neutral conditions [ 37 ]. To overcome the efficiency droop at a higher current density (>100 A cm –2 ), it is necessary to a subtly design the p-layer to improve the hole injection efficiency and the uniformity of the hole concentration within the well region of the MQWs, thereby avoiding Auger recombination as a result of a mismatch in the hole and electron concentrations.…”