We present latest development results of GaN based 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 blue LD showed the optical output power and the voltage of 5.25 W and 4.03 V at the forward current of 3 A under Continuous Wave (CW) operation. The wall plug efficiency of the blue LD was 43.4% at 3A. And pure green LDs at 532 nm showed the optical output power of 1.19 W and the wall plug efficiency of 17.1 % at the forward current of 1.6A. Furthermore, 543 nm green LDs were fabricated on C-plane GaN substrates.
We report our recent improvement of watt class blue and green GaN based LDs. These LDs were grown on c-face GaN substrates by metal organic chemical deposition. The laser chip was mounted on the heat sink by the junction down method in TO-ø9 mm package for the suppression of the thermal resistance. The optical output power of 455nm blue LDs was obtained above 4.7 W at injection current of 3A. The average lifetime was estimated to be over 30,000 hours at case temperature of 65 degree C under 3A. In green LDs, 1 watt class 532 nm green LDs as same wavelength as second harmonic generation (SHG) green laser was developed and the wall plug efficiency was 12.1 %. And the longer lasing wavelength was achieved to 537 nm.
The first-order AlInGaN 405 nm distributed feed-back (DFB) laser diodes were grown on the low dislocation freestanding
GaN substrates by a metal organic chemical vapor deposition method. The first-order diffractive grating whose
period was 80 nm was formed into an n-type cladding layer. The fine tooth shape grating was obtained by the EB
lithography and the dry etching. No additional threading dislocation could be found at the regrowth interface. As a result,
we succeeded in demonstrating the first-order AlInGaN based 405 nm DFB laser diodes under cw operation. The
threshold current and the slope efficiency were 22 mA and 1.44 W/A under continuous wave operation at 25 °C,
respectively. The single longitudinal mode emission was maintained up to an output power of 60 mW. The fundamental
transverse mode operation with a single longitudinal mode was observed in the temperature range from 15 °C to 85 °C at
an output power of 30 mW. The lifetime was estimated to be 4000 h by the lifetime test which was carried out under the
condition of a constant output power of 30mW at 25 °C for 1000 h. The single longitudinal mode emission was
maintained for the life tested DFB laser diodes.