Correlating vertical GaN PIN diode performance with micro-photoluminescence imaging

Vertical GaN p-i-n diode electrical performance metrics are examined and correlated with sub-bandgap micro-photoluminescence (μ-PL) mapping. Two hundred device locations were measured via μ-PL after the metalorganic chemical vapor deposition of the device structure on a near-equilibrium ammonothermal GaN substrate. Post-microfabrication of full PIN diodes, electrical measurements were correlated with the acquired μ-PL data. Turn-on voltage and breakdown voltage are examined and correlated with μ-PL maps of each device area. It was found that the overall threading-dislocation (TD) density did not correlate significantly with the breakdown voltage. However, the areal sizing of the TD features when clustered together can significantly impact and correlate with the expected breakdown voltage. It was found that the higher the number of counts of μ-PL features with areas greater than 5 μm2 in each device area, the lower the resultant breakdown voltage is for the device. The results obtained here can provide a basis for a high-throughput, non-destructive, in-line metrology method that can be used for predicting vertical GaN device performance prior microfabrication and testing in a mass-manufacturing environment immediately after epitaxial device growth.