
11GaN High-Voltage Power Devices
the test pad and the substrate provides the positive and negative branches of the verti-
cal leakage characteristics. Figure 1.5 shows a selection of vertical breakdown proles
taken from HEMT structures grown on buffer layers with different epitaxial designs.
The epitaxial layers were grown on n-type SiC wafers. Different buffer realizations
feature very unique vertical current ow properties, as represented by the respective
I/V characteristics. They differ in terms of symmetry between the positive branch and
the negative branch and the absolute value of maximum allowable vertical voltage in
the respective bra ...