Performance enhancement of AlGaN deep-ultraviolet light-emitting diodes with varied superlattice barrier electron blocking layer

Hole Transport Manipulation To Improve the Hole Injection for Deep Ultraviolet Light-Emitting Diodes

“…On the other hand, the optical power for DUV LEDs can be further enhanced if the hole blocking effect by the p-EBL is minimized. For that purpose, several alternative p-EBL structures have been proposed and demonstrated, such as superlattice-structured p-EBL, , AlGaN/AlGaN superlattice-structured last quantum barrier . The enhanced Mg doping efficiency by the superlattice structure can be partly ascribed to the generated resonant states in the wells according to the theoretical model proposed by Liu et al In addition, the hole transport across the conventional bulk AlGaN based p-EBL is mainly determined by the thermionic emission which is very sensitive to the Al composition in p-EBL.…”

Multiple fields manipulation on nitride material structures in ultraviolet light-emitting diodes

“…In 2014, Frank et al proposed Mg-doped AlN/Al 0.7 Ga 0.3 N electron blocking heterostructures with optimized AlN thickness to ensure charge carrier injection and suppress the electron leakage in sub-250 nm DUV LEDs 164 In 2015, Fan et al adopted inverted-V-shaped graded Al composition EBL to reduce the efficiency droop of DUV LED. Liu et al proposed an AlGaN SLs with varying barriers as the EBL of DUV LED, thereby causing the efficiency droop decreased from 80.8% to 28.8% 165 . In 2017 and 2018, Zhang et al modified the barrier height for EBL by utilizing p -Al 0.60 Ga 0.40 N (L2)/Al 0.50 Ga 0.50 N/ p -Al 0.60 Ga 0.40 N (L1) EBL and grading the alloy composition respectively, to guarantees a smooth hole injection into the active region 166 , 167 .…”

Deep-ultraviolet integrated photonic and optoelectronic devices: A prospect of the hybridization of group III–nitrides, III–oxides, and two-dimensional materials

“…Nevertheless, to realize efficient DUV optoelectronic devices, conductive p-type Al x Ga 1−x N layers are necessary. With limited success, there were several attempts to improve the conductivity and efficiency of p-Al x Ga 1−x N-based materials and devices through the incorporation of the following schemes: tunnel junctions (TJs) [170] , Al x Ga 1−x N/GaN superlattices (SLs) [171][172][173] , p-type graded Al x Ga 1−x N polar heterostructures [174][175][176][177][178] , Al x Ga 1−x N-delta-GaN QW structures [179,180] , and co-doping [181,182] . In 2017, Tran et al claimed to have experimentally accomplished remarkably high free hole concentrations of up to 6 × 10 17 cm -3 in magnesium-doped AlN nanowires at room temperature [183] , a value that is several orders of magnitude greater than those of conventional AlN epitaxial layers which are in the range of 10 10 cm -3 [115,162,167] , which in turn are several orders of magnitude lower than what is necessary to realize efficient LED and LD operation (10 17 -10 19 cm -3 ).…”