Ultraviolet Laser Diode on Nano-Porous AlGaN template
Tech ID: 33108 / UC Case 2023-870-0
Efficient AlGaN-based laser diodes (LDs) with emission wavelengths between 300nm and 370nm (UVA LDs) have numerous applications in the fields of lithography, 3D printing, curing, chemical sensing, cytometry, atmospheric LIDAR, and more. Lattice mismatches and dislocations are common obstacles that need to be addressed during the construction of UVA LDs. The devices can be formed on either low dislocation density HVPE-grown GaN substrates or AlN templates grown on sapphire substrates. The former method has yet to demonstrate a device with a suitable lifetime, a result of severe device cracking caused by tensile stress between the substrate and AlGaN layers. The latter method is opposed by the large lattice mismatch between the AlN template and the AlGaN active region when the emission wavelength of the LD is around 350~370nm, creating a large number of dislocations. Relieving either of these methods from their device growth drawbacks would enable a new generation of highly efficient, long-lasting laser devices that outpace their gas phase/solid-state counterparts by a wide margin.
Researchers at the University of California, Santa Barbara have overcome the pain points in constructing efficient ultraviolet laser diodes (UVA LDs) by using a separate confinement structure (SCH or waveguide layer) formed on a nano-porous n-AlGaN layer as the cladding layer. Nano-porous AlGaN has a much lower refractive index than that of a non-porous AlGaN layer with the same Al composition of the AlGaN. This consequently removes the condition to grow thick cladding layers with high Al composition. Instead, similar optical confinement can be achieved with thinner, lower-Al-content layers that can be easily formed on GaN substrates without cracking defects. In addition, the Al composition of the nano-porous n-AlGaN cladding layer is lower than that of conventional structure, which minimizes strain that would otherwise cause cracking defects and also minimizes the generation of new dislocation defects at the interface between the LD structure and nano-porous n-AlGaN cladding. This technology provides a superior structure and technique to fabricate UVA LDs on GaN substrates with dislocation densities of less than 1x106 cm-2 and a lifetime of over 10,000 hours.
- Prevents cracking and dislocations in UVA LDs formed on GaN substrates
- Enables long device lifetimes of over 10,000 hours
- Improved light confinement compared to alternative structures
- Laser Diodes
- Ultraviolet Laser Diodes (UVA LDs)
- 3D printing
- Chemical sensing
- Atmospheric LiDAR