Measurement of external stress on bulk GaN

We report on the measurement of stress in bulk, free-standing GaN templates under external bending using micro-Raman scattering. A 488 nm Ar-ion laser beam was scanned in a cross-sectional geometry across the GaN template held under external stress conditions. Our experiment showed that the top half of the bulk GaN was under ∼73 MPa of tensile stress while the bottom half of the GaN template was under 40 MPa of compressive stress when bent by a press screw. This data is very helpful to understand both the optical and mechanical properties of bulk GaN and for calibrating and optimizing GaN-based pressure sensors.