Enhancement of the optoelectronic characteristics of deep ultraviolet nanowire laser diodes by induction of bulk polarization charge with graded AlN composition in AlxGa1-xN waveguide

• Published in: Superlattices and microstructures Vol. 145; p. 106643
• Main Authors: Nawaz, Sharif Muhammad, Niass, Mussaab Ibrahim, Wang, Yifu, Xing, Zhongqiu, Wang, Fang, Liu, Yuhuai
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2020
• Subjects: AlN Composition grading; Induced bulk polarization; Nanowire laser diodes; Optical confinement factor; Waveguide; AlN Composition grading; Optical confinement factor; Nanowire laser diodes; Waveguide; Induced bulk polarization
• ISSN: 0749-6036; 1096-3677
• DOI: 10.1016/j.spmi.2020.106643

AlGaN based Nanowire laser diodes (NW-LDs) grown on sapphire substrates have strong polarization induced electric field. Such electric field has the ability to degrade the optoelectronic characteristics of deep ultraviolet (DUV) NW-LD. In this work, a graded AlN composition AlxGa1-xN waveguide (WG) layer is used for the enhancement of DUV NW-LD performance. Grading of WG induces bulk polarization charges which compensates the effect of polarization induced electric field. According to the calculated optoelectronic characteristics of NW-LD, it is found that grading of n-type WG (n-WG) increases the optical confinement factor (OCF) by 82%. Fortunately, the proposed graded n-WG structure suppresses the leakage of optical field from active region and enhances carrier injection efficiency. Furthermore, if both n-WG and p-WG graded layers are used, the improvement is not obvious because of the current leakage from graded p-WG. Thus, graded n-WG based NW-LD gives highest 33.5% OCF with the lowest 7 mA and 4.59 V threshold current and voltage respectively. •WG grading induces bulk polarization charge, which suppresses the field leakage from active media.•Grading of n-type WG (n-WG) increases the optical confinement factor (OCF).•As compared to the step graded WG and double graded WG structure, a single only graded n-WG NW-LD structure provides better performance.