Laser diodes grown on porous GaN by plasma-assisted molecular beam epitaxy

Abstract

Porous GaN has been proposed as a novel cladding material for visible light-emitting laser diodes (LDs). Fabrication of nanoporous-GaN bottom-cladding LDs was already realized by selective electrochemical etching (ECE) of the highly n-type doped GaN layer in the LD structure after epitaxy. In this work, we applied a reverse approach: in the first step, locally porous areas in GaN substrate were fabricated, and next, a LD structure was grown on top by plasma-assisted molecular beam epitaxy (PAMBE). We compare the electrical and optical properties of the devices with porous bottom cladding with the devices from the same wafer that was grown on top of a standard GaN layer. Continuous wave (CW) operation is achieved for porous LD at 435.4 nm and slope efficiency of 0.046 W/A. Standard LD was lased in CW mode at 442.6 nm and had a slope efficiency of 0.692 W/A. In porous LD, the internal losses were estimated using the Hakki-Paoli method to be 68 cm−1, while for standard LD, the losses were 25 cm−1. Near-field patterns recorded for the studied devices indicate light scattering on the porous layer to be the possible reason for the increased losses in porous LD.