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  • Küçük Resim Yok
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    Influence of sidewall grating etching depth on GaN-based distributed feedback laser diodes
    (Iop Publishing Ltd, 2024) Feng, Meixin; Li, Chuanjie; Tang, Yongjun; Liu, Jianxun; Sun, Xiujian; Liu, Qifa; Yilmaz, Ercan
    Conventional sidewall gratings in GaN-based distributed feedback (DFB) laser diodes (LD) have a thick p-type layer, which may cause current spreading and carrier-induced anti-guiding effects, severely deteriorating the lasers performance. In this study, we report a novel fabrication technology to not only reduce the remaining p-type layer in the sidewall gratings but also realize close-coupled sidewall gratings. Afterwards, we further investigate the influence of the sidewall gratings etching depth on GaN-based DFB LDs. The results show an almost unchanged current injection efficiency, nearly coincided I-V curve and a near-field emission width for shallow etched structures, which indicate that the current spreading is neglectable in GaN-based ridge structure LDs. Based on this analysis, GaN-on-Si DFB LDs with an emission wavelength of 414 nm, full width at half maxima of 22 pm, and side mode suppression ratio of 19.1 dB were realized.
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    Performance improvement of GaN-based microdisk lasers by using a PEALD-SiO2 passivation layer
    (Optica Publishing Group, 2023) Zhao, Hanru; Feng, Meixin; Liu, Jianxun; Sun, Xiujian; Li, Yongjian; Yılmaz, Ercan
    Dry-etching is often utilized to shape GaN-based materials. However, it inevitably causes plenty of sidewall defects as non-radiative recombination centers and charge traps that deteriorate GaN-based device performance. In this study, the effects of dielectric films deposited by plasma-enhanced atomic layer deposition (PEALD) and plasma-enhanced chemical vapor deposition (PECVD) on GaN-based microdisk laser performance were both investigated. The results demonstrated that the PEALD-SiO2 passivation layer largely reduced the trap-state density and increased the non-radiative recombination lifetime, thus leading to the significantly decreased threshold current, notably enhanced luminescence efficiency and smaller size dependence of GaN-based microdisk lasers as compared with the PECVD-Si3N4 passivation layer.
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    Ultrahigh-responsivity ultraviolet photodetectors based on AlGaN/GaN double-channel high-electron-mobility transistors
    (American Chemical Society, 2023) Wang, Haodong; Feng, Meixin; Zhong, Yaozong; Chen, Xin; Gao, Hongwei; Yılmaz, Ercan; Sun, Qian
    In this work, high-performance ultraviolet (UV) photodetectors (PDs) based on an AlGaN/GaN double-channel high-electron-mobility transistor (HEMT) were fabricated and investigated using 360 nm illumination. The design of the novel device structure introduces double two-dimensional electron gas channels, which remarkably improve the effectiveness in the collection of photo generated carriers and make it work as a two-terminal normally off device. The device exhibited a high responsivity of 2.1 x 10(7) A/W and a high specific detectivity of 1.7 x 10(15) Jones under the illumination of 9.7 mu W/cm(2), indicating the excellent capability of detecting an ultraweak signal. Meanwhile, a distinguished transient performance was also observed when it operated under 500 Hz pulse illumination. Combining fabrication conciseness and outstanding performance advantages, the proposed AlGaN/GaN double-channel HEMT UV PD shows promising potential in the development of next-generation UV PDs.