GaN-based violet laser diodes

Three kinds of substrates were used for violet InGaN multi- quantum-well/GaN/AlGaN separate-confinement-heterostructure laser diodes (LDs). One of substrates is epitaxially laterally overgrown GaN (ELOG) substrate. Another is `free- standing GaN' substrate. In order to obtain it, thick GaN was grown on `ELOG', and then, sapphire and `ELOG' were removed. Third one is `ELOG grown on thick GaN' substrate. The threading dislocation densities of `ELOG', `free- standing GaN' and `ELOG grown on thick GaN' were 1 X 10 6 /cm 2 , 5 X 10 7 /cm 2 and 7 X 10 5 /cm 2 , respectively. LDs were fabricated with the structure of epi side up. The estimated lifetime of LD grown on `ELOG grown on thick GaN' was 15000 h under condition of continuous-wave operation, case temperature of 60 degree(s)C and output power of 30 mW.