FLAAT Growth Technology for Low Cost Thick High Quality GaN on Thin 8 Sapphir

The use of non-native substrates for GaN- based devices leads to devices with high densities of defects stemming from misfit dislocation formation due to lattice mismatch and large values of wafer bow stemming from thermal mismatch. The latter is particularly problematic as one attempts to grow device films on large area substrates. The high defect densities give rise to degraded performance and reliability, while the wafer bow can be problematic to device fabrication as well as to growth of e.g. InGaN at lower temperatures than underlying buffer layer temperatures, reducing device yields. The technology proposed utilizes HVPE films grown on both sides of the wafer, which results in a bow-free, thick GaN template which is scalable to large diameter substrates. Templates are polished to an epi-ready finish, which is only possible when the wafers are flat in the first place. We have demonstrated the FLAAT concept using 2 and 4 sapphire for GaN thicknesses up to 50 microns. Initial LED results yielded lower wavelength distribution across a wafer than a control layer directly on sapphire. Phase II of this program will improve the structural, optical, and electrical properties of the templates as well as demonstrate the concept at 6. We will additionally demonstrate the concept using AlN films instead of GaN films. Commercial Applications and Other Benefits: The technology can provide the quality of freestanding GaN at the cost of a GaN template so many types of devices can be impacted by the availability of the FLAAT templates. The large area sapphire market would grow if the technology takes off.