Efficient tunnel junction contacts for high-power semipolar III-nitride edge-emitting laser diodes.

We demonstrate high-power edge-emitting laser diodes (LDs) with tunnel junction contacts grown by molecular beam epitaxy (MBE). Under pulsed conditions, lower threshold current densities were observed from LDs with MBE-grown tunnel junctions than from similarly fabricated control LDs with ITO contacts. LDs with tunnel junction contacts grown by metal-organic chemical vapor deposition (MOCVD) were additionally demonstrated. These LDs were fabricated using a p-GaN activation scheme utilizing lateral diffusion of hydrogen through the LD ridge sidewalls. Secondary ion mass spectroscopy measurements of the [Si] and [Mg] profiles in the MBE-grown and MOCVD-grown tunnel junctions were conducted to further investigate the results.

Continuous-wave operation of a semipolar InGaN distributed-feedback blue laser diode with a first-order indium tin oxide surface grating.

A novel approach to realize DFB gratings on GaN based laser diodes is presented and continuous-wave single longitudinal mode operation is achieved. The first order gratings were fabricated on the surface of indium tin oxide (ITO) on top of the laser ridge, which combines the benefits of simplified fabrication, easy scalability to wider ridges, and no regrowth or overgrowth. Under continuous-wave operation, the laser emits with a full FWHM of 5 pm, a SMSR of 29 dB and output power from a single facet as high as 80 mW. To the best of authors' knowledge, this is also the first demonstration of a DFB-LD on semipolar InGaN/GaN system.

Demonstration of enhanced continuous-wave operation of blue laser diodes on a semipolar 202¯1¯ GaN substrate using indium-tin-oxide/thin-p-GaN cladding layers.

The benefits of utilizing transparent conductive oxide on top of a thin p-GaN layer for continuous-wave (CW) operation of blue laser diodes (LDs) were investigated. A very low operating voltage of 5.35 V at 10 kA/cm2 was obtained for LDs with 250 nm thick p-GaN compared to 7.3 V for LDs with conventional 650 nm thick p-GaN. An improved thermal performance was also observed for the thin p-GaN samples resulting in a 40% increase in peak light output power and a 32% decrease in surface temperature. Finally, a tradeoff was demonstrated between low operating voltage and increased optical modal loss in the indium tin oxide (ITO) with thinner p-GaN. LDs lasing at 445 nm with 150 nm thick p-GaN had an excess modal loss while LDs with an optimal 250 nm thick p-GaN resulted in optical output power of 1.1 W per facet without facet coatings and a wall-plug efficiency of 15%.