InGaN based green laser diodes on semipolar GaN substrate

This paper reviews the development of the InGaN-based green laser diodes on semipolar GaN substrates, especially focusing on (20 (2) over bar1) plane. The reduction of piezoelectric fields in InGaN quantum wells on the (20 (2) over bar1) planes was investigated by a small blue shift in electroluminescence peaks, and high crystal quality was confirmed by clear interfaces in a transmission electron microscopy image, narrower FWHM in electroluminescence peaks, and smaller localization energy in time resolved PL results, as compared with the other planes. These physical characteristics of the (20 (2) over bar1) leads to better laser properties: lower threshold current densities, higher output powers of over 100 mW in the spectral region beyond 530 nm, and higher wall plug efficiencies as high as 7.0-8.9% in the wavelength range of 525-532 nm, compared to those of the other planes. Estimated lifetimes were over 5000 h at 50 mW and 2000 h at 70 mW under cw operation with auto power control at a case temperature of 55 degrees C. The (20 (2) over bar1) plane is the promising candidate for InGaN-based true green laser diodes. (C) 2014 The Japan Society of Applied Physics