Demonstration of Electrically Injected Semipolar Laser Diodes Grown on Low-Cost and Scalable Sapphire Substrates

Abstract

The last two decades have shown an increasing need for GaN-based laser diodes (LDs), which are currently only grown on bulk GaN substrates, which remain to date very expensive and/or only available in small sizes. The ever growing laser market will expand in the coming years, thanks to the development of automotive laser lighting, high-speed Li-Fi optical data transmission, LiDAR sensing for autonomous vehicles and smart cities, head-up displays, and AR/VR systems, in addition to biomedical and further industrial applications. These emerging technologies demand for mass-production of GaN-based lasers to be produced on large-size, low-cost, and industrially compatible substrates. To address this issue, we demonstrate the first electrically injected semipolar 440 nm LD on high-quality and low-defect-density (11−22) GaN templates grown on scalable and low-cost sapphire substrates. The LDs exhibit a threshold current density of 17 kA/cm 2 , a single facet output power of more than 200 mW at 2 A with a slope efficiency of 0.85 W/A, and a TE polarization having a ratio of 97.6%. These results enable the advancement of ultra-low-cost LDs while benefiting from the inherent advantages of semipolar GaN properties.

MOCVD growth of thick V-pit-free InGaN films on semi-relaxed InGaN substrates

“…The piezoelectric polarization then leads to the quantum confined stark effect (QCSE), where the electron and hole wavefunctions separate within the QWs, causing further reduction in the internal quantum efficiency (IQE) [8]. Alternative GaN orientations such as semipolar and nonpolar have shown promise to push towards longer wavelength by reducing the effective polarization in the direction of charge flow, but a challenge remains in scalability of such substrates as they remain available only in very small sizes at very high prices [9][10][11][12].…”

Влияние морфологии буферного слоя AlN на структурное качество полуполярного слоя GaN, выращенного на подложке Si(001), по данным просвечивающей электронной микроскопии

“…Это проявляется в относительно низкой плотности прорастающих дислокаций (4 • 10 9 cm −2 на расстоянии 2 µm от интерфейса и 3 • 10 8 cm −2 у поверхности слоя GaN [17]). При использовании гораздо более дорогостоящего метода маскирования подложки была достигнута плотность 5 • 10 7 cm −2 [18]. При этом следует учитывать, что в качестве подложки был выбран сапфир, а не Si(001), позволяющий легко интегрировать метод в кремниевую технологию.…”

Demonstration of Efficient Semipolar 410 nm Violet Laser Diodes Heteroepitaxially Grown on High-Quality Low-Cost GaN/Sapphire Substrates

“…The first semipolar blue LDs on a foreign substrate were realized on a high-crystal-quality (112̅ 2) GaN/sapphire template. 18 Nevertheless, their performance was still far from satisfactory because of the high threshold current density (J th ) of 17 kA cm −2 , a threshold voltage of over 11.5 V, and a low wall-plug efficiency (WPE) of 1.5%. Further investigation of the performance of these LDs on foreign substrates is necessary, and a full understanding of the internal material parameters such as optical loss and material gain of these LDs is thus highly desired.…”

“…To date, however, semipolar LDs have been achieved only on costly small-area semipolar bulk GaN substrates, limiting their wide use. Realization of low-cost semipolar LDs by heteroepitaxial growth is appealing, − but the efficiency of semipolar LEDs grown on foreign substrates remains poor because of the high dislocation defect density. − The best external quantum efficiency (EQE) of semipolar blue LEDs is only 6%, which is still much lower than that of semipolar blue LEDs on a bulk GaN substrate or conventional c-plane blue LEDs. On the other hand, the development of semipolar LDs on foreign substrates is even more challenging.…”

“…On the other hand, the development of semipolar LDs on foreign substrates is even more challenging. The first semipolar blue LDs on a foreign substrate were realized on a high-crystal-quality (112̅2) GaN/sapphire template . Nevertheless, their performance was still far from satisfactory because of the high threshold current density ( J th ) of 17 kA cm –2 , a threshold voltage of over 11.5 V, and a low wall-plug efficiency (WPE) of 1.5%.…”