High-power and long-lifetime InGaN multi-quantum-well laser diodes grown on low-dislocation-density GaN substrates

Epitaxially laterally overgrown GaN on free-standing GaN was used-to reduce the threading dislocations which were widely scattered over the entire surface. The threading dislocation density of the GaN layer above the window area surrounding the SiO2 mask was reduced to 5 x 10(7)/cm(2), and that of the GaN layer above the SiO2 mask area was reduced to 7 x 10(5)/cm(2). InGaN multi-quantum-well laser diodes (LDs) grown on low-dislocation-density GaN substrates were demonstrated. LDs with an output power of 30 mW exhibited an estimated lifetime of 15,000 h at a case temperature of 60 degrees C. At a case temperature of 25 degrees C, the current at the output power of 30 mW and at the lasing threshold current were 42 mA and 23 mA, respectively. For comparison, LDs were grown on different substrates, and the dependence of their characteristics on the substrates was examined.