Electrically pumped blue laser diodes with nanoporous bottom cladding

Abstract

We demonstrate electrically pumped III-nitride edge-emitting laser diodes (LDs) with nanoporous bottom cladding grown by plasma-assisted molecular beam epitaxy on c-plane (0001) GaN. After the epitaxy of the LD structure, highly doped 350 nm thick GaN:Si cladding layer with Si concentration of 6·1019 cm-3 was electrochemically etched to obtain porosity of 15 ± 3% with pore size of 20 ± 9 nm. The devices with nanoporous bottom cladding are compared to the reference structures. The pulse mode operation was obtained at 448.7 nm with a slope efficiency (SE) of 0.2 W/A while the reference device without etched cladding layer was lasing at 457 nm with SE of 0.56 W/A. The design of the LDs with porous bottom cladding was modelled theoretically. Performed calculations allowed to choose the optimum porosity and thickness of the cladding needed for the desired optical mode confinement and reduced the risk of light leakage to the substrate and to the top-metal contact. This demonstration opens new possibilities for the fabrication of III-nitride LDs.

All-BN distributed Bragg reflectors fabricated in a single MOCVD process

“…For both BN layers, the refractive index for wavelengths above 500 nm may be treated as slowly varying, therefore the refractive index contrast is almost constant, at an average of 0.17. This value is on a similar level as the refractive index contrast of porous and non-porous GaN layers used in DBRs [34,35]. Furthermore, for this wavelength range, the imaginary part of the refractive index is negligible, therefore the layers may be treated as non-absorbing.…”

“…Another approach to obtain the needed reflective index contrast is to use porous structures. However, such structures require a selective post-fabrication etching process [30][31][32][33][34][35].…”