[1] A Khan, K Balakrishnan, T Katona. Ultraviolet light-emitting diodes based on group three nitrides. Nat Photonics, 2, 77(2008).
[2] D Li, K Jiang, X Sun et al. AlGaN photonics: recent advances in materials and ultraviolet devices. Adv Opt Photonics, 10, 43(2018).
[3] T Takano, T Mino, J Sakai et al. Deep-ultraviolet light-emitting diodes with external quantum efficiency higher than 20% at 275 nm achieved by improving light-extraction efficiency. Appl Phys Express, 10, 031002(2017).
[4] J Hodgkinson, R P Tatam. Optical gas sensing: a review. Meas Sci Technol, 24, 012004(2013).
[5] E Allaria, D Castronovo, P Cinquegrana et al. Two-stage seeded soft-X-ray free-electron laser. Nat Photonics, 7, 913(2013).
[6] M Kneissl, T Y Seong, J Han et al. The emergence and prospects of deep-ultraviolet light-emitting diode technologies. Nat Photonics, 13, 233(2019).
[7] Z Zhang, M Kushimoto, T Sakai et al. A 271.8 nm deep-ultraviolet laser diode for room temperature operation. Appl Phys Express, 12, 124003(2019).
[8] K Ban, J I Yamamoto, K Takeda et al. Internal quantum efficiency of whole-composition-range AlGaN multi-quantum wells. Appl Phys Express, 4, 052101(2011).
[9] M Kneissl, T Kolbe, C Chua et al. Advances in group III-nitride-based deep UV light-emitting diode technology. Semicond Sci Technol, 26, 014036(2011).
[10] J Simon, V Protasenko, C Lian et al. Polarization-induced hole doping in wide-band-gap uniaxial semiconductor heterostructures. Sciences, 327, 60(2009).
[11] H Chang, Z Chen, W Li et al. Graphene-assisted quasi-van der Waals epitaxy of AlN film for ultraviolet light emitting diodes on nano-patterned sapphire substrate. Appl Phys Lett, 114, 091107(2019).
[12] H Hirayama, T Yatabe, N Noguchi et al. 231–261 nm AlGaN deep-ultraviolet light-emitting diodes fabricated on AlN multilayer buffers grown by ammonia pulse-flow method on sapphire. Appl Phys Lett, 91, 71901(2007).
[13] W Tian, W Y Yan, J N Dai et al. Effect of growth temperature of an AlN intermediate layer on the growth mode of AlN grown by MOCVD. J Phys D, 46, 065303(2013).
[14] M Shatalov, W Sun, A Lunev et al. AlGaN deep-ultraviolet light-emitting diodes with external quantum efficiency above 10%. Appl Phys Express, 5, 082101(2012).
[15] M Djavid, Z Mi. Ehancing the light extraction efficiency of AlGaN deep ultraviolet light emitting diodes by using nanowire structures. Appl Phys Lett, 108, 051102(2005).
[16] S R Jeon, Z Ren, G Cui et al.
[17] M L Nakarmi, K H Kim, J Li et al. Enhanced p-type conduction in GaN and AlGaN by Mg-δ-doping. Appl Phys Lett, 82, 3041(2003).
[18] H X Zhong, J J Shi, M Zhang et al. Improving p-type doping efficiency in Al0.83Ga0.17N alloy substituted by nanoscale (AlN)5/(GaN)1 superlattice with MgGa-ON δ-codoping: Role of O-atom in GaN monolayer. AIP Adv, 5, 227(2015).
