Blue and green InGaN semiconductor lasers as light sources for displays
Yoshitaka Nakatsu, Yoji Nagao, Tsuyoshi Hirao, Yoshihiro Hara, Shingo Masui, Tomoya Yanamoto, Shin‐ichi Nagahama
Abstract
This paper reports the latest device performance of high-power blue and green Laser Diodes (LDs). The epitaxial structures of LDs including n-type, active and p-type layers were grown by metal organic chemical vapor deposition (MOCVD) on C-plane free-standing GaN substrates. And a ridge type structure and Electrodes of the n-type and p-type were formed. Front and rear mirror facets were obtained by cleavage at the m-plane surface. We optimized the epitaxial and the device structures for high efficiency, high optical output power and reliability. Every LD chip was mounted on a heat sink using a junction down method in a TO-Φ9 mm package for suppressing thermal resistance. A New developed 455 nm blue LD showed the optical output power and the voltage of 5.67 W and 3.93 V at the forward current of 3 A under Continuous Wave (CW) operation. The wall plug efficiency of the 455 nm blue LD was 48.1% at 3A. The wall plug efficiency of the high-power blue LD we developed is the highest reported so far. A new developed green LD at 525 nm showed the optical output power of 1.75 W and the wall plug efficiency of 21.2 % at the forward current of 1.9A. The optical output power, the voltage and the wall plug efficiency of a new 532 nm LD showed 1.53 W and 4.35 V, 18.5 % at the forward current of 1.9 A under CW operation. The peak wall plug efficiency of the 532 nm LD was 20 % at the optical output power of 1W.