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 NA 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. (C) 2017 The Japan Society of Applied Physics