Carrier Transport Mechanism via a High-k HfO₂ Thin Layer Between GaAs Layers

Carrier transport mechanisms via a high-k gate dielectric material of hafnium dioxide (HfO2) between III-V GaAs were investigated by using a non-equilibrium Green's function (NEGF). The full band structure for the HfO2 layer was determined by using a sp3d5s* closest neighbor empirical tight-binding model. The band structure of the GaAs bulk was determined by using an empirical tight-binding model. The tunneling currents dependent on the thickness of the HfO2 layer with a GaAs layer were obtained by solving the NEGF in an open boundary condition. The applied voltage to obtain the tunneling currents through the HfO2 layer between the GaAs layers was higher than that for the Si/HfO2/Si structure. This was due to the much smaller energy difference between the conduction band edge (Ec) and the Fermi level (Ef) of the Si layer than that of the GaAs layer. The GaAs/HfO2/GaAs structure showed an increase in the leakage current in comparison with the Si/HfO2/Si structure.