Experimental investigation on dipole and band offset affected by charge neutrality level modulation

Band alignment has been keeping fascinating because of its importance to the heterojunction interface for engineering the device performances. One of the most crucial parameters to determine band alignment is the charge neutrality level (CNL). In this study, we experimentally investigate the CNL modulation from the perspective of dipole formation at the GeO2/Al2O3 interface and conduction band offset (CBO) tendency with Al2O3 thicknesses after post-deposition annealing (PDA). The core level shift at the GeO2/Al2O3 interface consists with the dipole change for the as-grown and N-2 PDA samples. The origin of dipole change after PDA is explained through CNL theory and band alignment. The CNL modulation is certified from the CBO dependence on the Al2O3 thickness. The CBO at Ge/Al2O3 hetero-interface decreases with Al2O3 thickness for the as-grown sample and increases with Al2O3 thickness after N-2 annealing. The CNL was experimentally estimated as 4.57 and 3.52 eV above the Al2O3 valence band maximum for the as-grown and N-2 PDA samples. The CNL estimation is also consistent with the modulation change of dipole at the Al2O3/GeO2 interface and CBO at Ge/Al2O3 interface. This research may provide a feasible method of promoting device performance by modulating the CNL of dielectrics.

Automated summary

This study experimentally investigates the modulation of CNL through dipole formation at the GeO2/Al2O3 interface and the influence of Al2O3 thickness on CBO. The results show that adjusting CNL can enhance the performance of dielectrics.