Direct observation of cross-sectional potential distribution in GaN-based MIS structures by Kelvin-probe force microscopy

Cross-sectional potential distribution in GaN-based trench gate metal-insulator-semiconductor field-effect transistors (MISFET) at off-and operating-state has been investigated by using Kelvin-probe force microscopy to clarify the actual operating situation of trench gate MISFET. The potential distribution reflecting the wafer structure, n/p/n(-)/n(+), is observed as shown in the right figure. At the off-state (the gate voltage is fixed to 0 V), it is found that the electric field at the internal p/n(-) interface become strong, on the contrary to that at top n/p interface is almost unchanged by the stepwise increase of the drain bias from 0 to 15 V. From the analysis of results obtained at operating state, we can confirm the situation how the channel forms by increasing the gate voltage. This information is useful for designing devices and improving their characteristics. [GRAPHICS] (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim