Skip to Main Content
We analyze the fixed oxide charge in Al2O3 grown by thermal and plasma enhanced ALD at 100 and 200 °C using capacitance-voltage measurements on MOS structures with different Al2O3 thickness. For both ALD techniques and deposition temperatures, Al2O3 shows negative fixed oxide charge with density in the range of 2-7×1012 cm-2, most likely located at the Al2O3/SiO2 interface as inferred from the linear dependence of flat-band voltage on Al2O3 thickness. The break-down field ranges from 4 to 8 MV/cm illustrating a high quality of the Al2O3 layers. Post-deposition annealing was found to stabilize the Al2O3 dielectric constant determined to be similar to 9. Control of the negative Al2O3 fixed charge represents a promising way to e.g. enhance the threshold voltage shift of GaN based MOS heterostructure FETs towards normally-off operation.