Unified analytic model of direct and Fowler–Nordheim tunnel currents through ultrathin gate oxides

A theoretical model to predict the gate tunnel current in metal–oxide–semiconductor structures has been developed by employing the nonparabolic E-k dispersion for describing the tunneling electron momentum. The tunnel electron effective mass mox and the Fermi energy in the gate have been used to fit the calculated tunnel current to the measured one. It is shown that in the direct tunneling regime the tunnel electron effective mass mox apparently increases with decreasing oxide thickness presumably due to the reduction of Si–O–Si bond angle in the compressively strained layer near the SiO2/Si interface, while in the Fowler–Nordheim tunneling regime mox remains constant at 0.50 m0.