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DS: Fachverband Dünne Schichten

DS 55: Focused Session: Novel Green Laser Diodes (jointly with HL and O)

DS 55.4: Invited Talk

Thursday, March 17, 2011, 16:15–16:45, POT 51

Advantages of Using Semipolar Orientation for Making Green InGaN QW Laser Diodes. — •Dmitry Sizov, Rajaram Bhat, Kechang Song, and Chung-en Zah — Corning Incorporated, One Science Center Dr., Corning, NY, 14831, USA

During recent years, several research groups demonstrated a steady progress in increasing InGaN quantum well (QW) laser diode lasing wavelength. Using c-plane substrates has been a preferred approach for it, thanks to established growth and fabrication techniques and available 2-inch substrates. More lately, semipolar substrates became available enabling faster progress in this field. Theoretical and experimental studies show that in green spectral range, because of lower built-in electric fields, the differential gain of semipolar QW is much higher than in c-plane if the stripe direction is properly chosen. For this, one needs to take into account that emission polarization depends not only on QW plane orientation, but also on pumping level. Another advantage of semipolar orientation is easier carrier transport in green semipolar multiple-QWs due to smoother band profile resulting from reduced pizeoelectrical effect, allowing uniform carrier injection among QWs when using more QWs to increase net optical gain. While having the improved optical gain, we found that the internal optical losses are not a strong function of substrate orientation, but rather depend on acceptor concentration in p-layers. Both quantum efficiency and optical gain can however be altered by strain relaxation, which is prone in the semipolar system, but can be avoided via proper strain management.