Long lifetime cw InGaN laser diodes by molecular beam epitaxy

Abstract

The growth and fabrication of 405 nm InGaN laser diodes by molecular beam epitaxy (MBE) has made rapid progress over the last three years. In 2004, the authors reported the first MBE-grown nitride laser diodes. In mid-2005 the authors then demonstrated room-temperature continuous-wave (cw) operation. This was achieved by significantly reducing the threshold current density to 5.6 kA/cm 2 for facet-coated LDs. The lifetime of these first MBE-grown cw lasers was up to 3 minutes, limited by power dissipation. In this paper we report on the progress we have made in reducing operating voltage and power dissipation, enabling a significant increase in laser lifetime. Uncoated 2x1000 mm ridge waveguide lasers fabricated on freestanding GaN substrates have a continuous-wave (cw) threshold current of 110 mA, corresponding to a threshold current density of 5.5 kA/cm 2 . For 2x600 mm laser diodes the minimum threshold current is 70 mA. Cw laser lifetime vs. power dissipation data is presented, with a maximum lifetime of 2.6 hours for the best laser. The lifetime versus power dissipation data shows that the MBE-grown lasers follow a similar trend as lasers grown by metalorganic chemical vapor deposition (MOCVD). We also report length dependence measurements of these long lifetime lasers, with a gain G 0 of 2000-2200 cm -1 and an internal loss a i =30-45 cm -1 .