  The interfacial band configuration of the high-k dielectric Al$_2$O$_3$
deposited at 120{\deg}C by atomic layer deposition (ALD) on boron- and
phosphorus-doped hydrogen-terminated (111) diamond was investigated. Performing
X-ray photoelectron spectroscopy measurements of core level binding energies
and valence band maxima values, the valence band offsets of both
heterojunctions are concluded to be {\Delta}E$_V$ = 1.8 eV and {\Delta}E$_V$ =
2.7 eV for the Al$_2$O$_3$/H(111)p and the Al$_2$O$_3$/H(111)n respectively.
The ALD Al$_2$O$_3$ bandgap energy was measured from the O 1s photoelectron
energy loss spectra to be $E_G^{ Al_2O_3}$ = 7.1 eV. The interfacial band
diagram configuration is concluded to be of type II for both
Al$_2$O$_3$/H(111)p and Al$_2$O$_3$/H(111)n heterostructures having conduction
band offsets of {\Delta}E$_C$ = 0.2 eV and {\Delta}E$_C$ = 1.1 eV respectively.
The use of doped (111) hydrogen-terminated diamond for developing future
diamond MOSFET is discussed.
