Deep ultraviolet emitting AlGaN quantum wells with high internal quantum efficiency

Abstract

We report the development of Al 0.7 Ga 0.3 N / AlN quantum wells with high internal quantum efficiency. All samples had identical well and barrier thickness but the III/V flux ratio was varied during growth by increasing the Ga flux. The luminescence spectra show single peaks which vary from 220 nm ͑III/ V ϳ 1͒ to 250 nm ͑III/ V ӷ 1͒ with internal quantum efficiency varying from 5% to 50%, respectively. To account for these results, a growth model was proposed in which at III/ V ϳ 1 the growth proceeds via vapor phase epitaxy, while at III/ V ӷ 1 the growth proceeds via liquid phase epitaxy.

Tunnel junction enhanced nanowire ultraviolet light emitting diodes

“…AlGaN based light emitting diodes (LEDs) are the main source for solid state UV emitters mainly because of the wide range of direct band gaps spanning the UVA, UVB, and UVC range [2]- [6].…”

Deep-UV emission at 219 nm from ultrathin MBE GaN/AlN quantum heterostructures

“…dislocation) induced non-radiative recombination. Compositional fluctuations of Al and Ga concentrations in ternary AlGaN alloy layers degrade efficient optical emission in the deep-UV range [12], and together with the other effects degrade the LED efficiency.Distinct from the alloy AlGaN layers, deep-UV emission down to 224 nm has been achieved in binary GaN/AlN heterostructures [13][14][15][16][17]. As a significant advantage, the polarization of the emitted photons in ultrathin GaN QWs and quantum dots/disks (QDs) is perpendicular to the c axis, making them propagate parallel to the c-axis [9,11]; this surface emission property is highly favorable for light extraction.…”

“…dislocation) induced non-radiative recombination. Compositional fluctuations of Al and Ga concentrations in ternary AlGaN alloy layers degrade efficient optical emission in the deep-UV range [12], and together with the other effects degrade the LED efficiency.…”

Ultraviolet light emitting diodes

“…In general, IQE decreases with increasing Al content. For example, in AlGaN/AlN MQWs, IQE was estimated to be 50% and 5% for the structures emitting at 250 nm and 220 nm, respectively [101]. Note, however, that the absolute IQE values, as discussed above, reflect the upper limit of the real values and might be considerably lower than the values reported.…”