GaN-based high-power laser diodes (LDs) have attracted tremendous interests in next-generation lighting applications, such as laser display, car laser light. However, high injection current usually brings inevitable drawbacks, including the well-known efficiency droop, Auger recombination and self-heating which obstruct further improvements of GaN-based optoelectrical devices. In this paper, influence of hole overflow at high injection current in an asymmetric GaN-based highpower blue LD has been comprehensively investigated and successfully suppressed by employing a new sandwiched GaN/AlGaN/GaN lower quantum barrier (GAG-LQB). Systematical simulations and measurements of structural and optical properties are carried out. As a result, the V-shaped defects induced by thick n-InGaN waveguide layer are apparently eliminated, which provides a more growth-friendly platform for deposition of the rest epitaxial layers and thus a better crystalline quality is obtained. On the other hand, the modified LD exhibits better photo-electrical properties with slope efficiency (SE) increasing from 0.98 to 1.24 and wall-plug efficiency (WPE) increasing from 18.7% to 20.5% at a high current of 1.5 A and no obvious efficiency droop is observed at a current as high as 2 A compared with the conventional one, because the middle-inserted AlGaN layer could form an extra barrier on the valence band to weaken the hole overflow and enhance the radiative recombination. Furthermore, the in-plane compressive strain induced by InGaN quantum wells (QWs) is also partially compensated by the tensile strain induced by the AlGaN layer. Therefore, the piezoelectric fieldinduced polarization is effectively alleviated and the wavelength blueshift is reduced from 7 nm to 1.6 nm.
Tian Lan, Guangzheng Zhou, Congcong Wang, Ying Li, Rui Huang, Anru Yan, and Zhiyong Wang, "Influence of sandwiched GaN/AlGaN/GaN lower quantum barrier on crystallinity and luminescence of an asymmetric GaN-based high-power laser diode," Proc. SPIE 10918, Gallium Nitride Materials and Devices XIV, 109181F (Presented at SPIE OPTO: February 06, 2019; Published: 1 March 2019); https://doi.org/10.1117/12.2502649.
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