Wafer-level nondestructive inspection of substrate off-angle and net donor concentration of the n − -drift layer in vertical GaN-on-GaN Schottky diodes

In the mass production of GaN-on-GaN vertical power devices, a nondestructive simple inspection of the net donor concentration ( N D − N A ) of the n − -drift layer in the range of 10 15 cm −3 is required. In this study, we demonstrate the wafer-level nondestructive inspection of GaN Schottky barrier diode epi-structures grown by metal organic vapor phase epitaxy (MOVPE) on free-standing GaN substrates. We found that the normalized yellow (YL) photoluminescence peak intensity of the near band edge (NBE), I YL / I NBE , is strongly related to the acceptor concentration N A of the n − -drift layer. This means that the N D − N A of the n − -drift layer can be inspected by photoluminescence measurement at a high speed, when Si concentration is not varying across the GaN wafers. Noncontact capacitance–voltage and secondary ion mass spectrometry measurements were used to investigate the cause of N D − N A variation across the GaN wafers. The discrepancy between C and N A indicates that compensation could be due to another electron trap.