Bias dependent band alignment in Ga₂O₃ ferroelectric interface by operando HAXPES

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• Gallium oxide (Ga2O3) is a wide band gap semiconductor with potential for power electronics.
• Germanium (Ge) is explored as an n-type dopant for Ga2O3 due to its shallow donor level and favorable growth.
• Hafnium Zirconium Oxide (HZO) is a ferroelectric material with potential applications in memory and logic devices.

Purpose of the Study:

• To investigate the band alignment at the interface of HfZrO4 (HZO) and Ge-doped Ga2O3.
• To understand the impact of Ge doping on Ga2O3 properties for HZO integration.
• To explore the feasibility of utilizing ferroelectric polarization in HZO for device applications.

Main Methods:

• Hard X-ray Photoelectron Spectroscopy (HAXPES) with in situ bias application to measure band alignment.
• High-Resolution Transmission Electron Microscopy (HRTEM) for structural characterization.
• Electrical characterization to assess charge injection and trapping.

Main Results:

• Structural analysis confirmed the polar orthorhombic phase of HZO.
• Electrical characterization revealed charge injection and trapping at the HZO/Ga2O3 interface.
• These interfacial issues prevent the stabilization of ferroelectric polarization in HZO.
• The band alignment is dominated by bias-induced band skewing due to a leaky HZO layer.

Conclusions:

• The integration of HZO with Ge-doped Ga2O3 faces challenges due to interfacial charge effects.
• Ferroelectric polarization in HZO is not stabilized under these conditions.
• The band alignment is significantly influenced by applied bias, leading to band skewing.