An important dispersion in the Rsheet measurement of AlGaN/GaN wafers was found on different samples, with or without SiN passivation. The dispersion is due to a drift of the Rsheet appearing when the sample is placed in the dark. This drift is different for each sample and it is caused by a trapping mechanism. A constant measurement of the Rsheet can be obtained under illumination. Thus, two parameters deserve measurement for an efficient screening of a technology: Rsheet under light and ΔRsheet in obscurity.
•We study the dispersion in the Rsheet measurement.
•We study the light influence on the Rsheet measurement.
•We deduce a trapping mechanism in the AlGaN/GaN stack.
•We simulate the trapping phenomenon.
Source: Microelectronic Engineering