Investigation on Surface Polarization of Al2O3-capped GaN/AlGaN/GaN Heterostructure by Angle-Resolved X-ray Photoelectron Spectroscopy

Table 1 Summary of the BEs (eV) of Ga 3d and Al 2p at different detection angles for all the samples, with the error of ± 0.1 eV

Samples	Core level	Chemical bonds	Detection angles θ
Samples	Core level	Chemical bonds	27.5°	42.5°	57.5°	72.5°
S1	Ga 3d	Ga–N	20.2	20.1	20.1	20.0
	Ga 3d	Ga–O	21.2	20.8	20.8	20.8
	Al 2p	Al–O	74.7	74.7	74.7	74.7
S2	Ga 3d	Ga–N	20.1	20.0	20	20.0
	Ga 3d	Ga–O	20.8	20.8	20.6	20.7
	Al 2p	Al–O	74.6	74.7	74.7	74.7
S3	Ga 3d	Ga–N	20.0	20.2	20.2	20.2
	Ga 3d	Ga–O	20.9	20.8	20.9	20.9
	Al 2p	Al–O	74.7	74.7	74.7	74.6