Non-planar growth of high Al-mole-fraction AlGaN heterostructures on patterned GaN substrates for ultraviolet laser diodes

The non-planar growth of UV-A laser diode heterostructures composed of AlGaN layers with high Al-mole-fractions and thicknesses exceeding the critical layer thickness was performed on patterned c-plane GaN (0001) substrates with stripe-shaped mesa structures. This approach suppressed the surface cracking at the top of the mesas via an anisotropic relaxation of the in-plane strain along the direction normal to the mesa stripes. Stimulated emission and laser operation at room temperature with emission in the UV-A range under pulsed current injection were demonstrated for laser diodes fabricated on the mesas.