Abstract
The p-AlGaN/AlGaN superlattice (SL) hole injection structure was introduced into deep ultraviolet (DUV) light-emitting diodes (LEDs) to enhance their performances. The period thicknesses of the p-Al0.8Ga0.2N/Al0.48Ga0.52N SLs affected the performances of the DUV LEDs. The appropriate period thickness of the p-Al0.8Ga0.2N/Al0.48Ga0.52N SL may enhance the hole injection of DUV LEDs. Therefore, compared with the reference LEDs, the DUV LEDs with the 10-pair Al0.8Ga0.2N (1 nm)/Al0.48Ga0.52N (1 nm) SL presented forward voltage reduction of 0.23 V and light output power improvement of 15% at a current of 350 mA. Furthermore, the 10-pair Al0.8Ga0.2N (1 nm)/Al0.48Ga0.52N (1 nm) SL could slightly suppress the Auger recombination and current overflow of the DUV LEDs in a high-current operation region. In addition to improved carrier injection, the DUV LEDs with the p-Al0.8Ga0.2N/Al0.48Ga0.52N SL hole injection structure showed reduced light absorption at their emission wavelength compared with the reference LEDs. Therefore, the DUV LEDs with p-Al0.8Ga0.2N/Al0.48Ga0.52N SL may exhibit better light extraction efficiency than the reference LEDs. The enhancement of p-Al0.8Ga0.2N (1 nm)/Al0.48Ga0.52N (1 nm) SL may contribute to improvements in light extraction and hole injection.
Highlights
AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) have attracted attention in many fields, such as ultraviolet photolithography, high-density optical data storage, water purification, and portable chemical/biological agent detection/analysis systems [1,2,3,4,5]
Despite the dramatic improvements in DUV LED performance, AlGaN-based DUV LEDs continue to face the problems of high-defect density and low-hole concentrations of high Al-content AlGaN material
A 20 nm thick Mg-doped Al0.48Ga0.52N hole injection layer was grown on the electron blocking layer (EBL) for the standard DUV LEDs as a reference
Summary
AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) have attracted attention in many fields, such as ultraviolet photolithography, high-density optical data storage, water purification, and portable chemical/biological agent detection/analysis systems [1,2,3,4,5]. Despite the dramatic improvements in DUV LED performance, AlGaN-based DUV LEDs continue to face the problems of high-defect density and low-hole concentrations of high Al-content AlGaN material. Since the initial study on GaN-based LEDs, the low-hole concentrations of p-type GaN-based material has been a major issue that limits the efficiency of GaN-based LEDs because it causes poor hole injection [12,13,14,15,16,17]. The problem of low-hole concentration for p-type AlxGa1−xN with x > 0.5 is worsening [10,11,12,13]. The doping efficiency for AlGaN with high Al content is still far from satisfactory due to a combination of factors involving limited solubility, high activation energy, increased donor compensations, and increased hole scatterings [14,15]. The p-type AlGaN/GaN heterojunction [18,19,20] and the AlGaN/GaN superlattice (SL) [21,22,23,24,25,26,27,28] have been reported to increase the hole concentrations of p-type
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