Physical and electrical properties of a Si₃N₄/Si/GaSs metal-insulator-semiconductor structure

We simulated capacitance-voltage (C-V) curves of Si₃N₄/GaAs, Si₃N₄/Si and also Si₃N₄/Semi* (virtual semiconductor) metal-insulator-semiconductor (MIS) capacitors and compared them with experimental C-V curves of a Si₃N₄/Si/GaAs structure. The experimental C-V curves of the Si₃N₄/Si/GaAs MIS capacitors are not in agreement with the simulated C-V curves of the Si₃N₄/GaAs and Si₃N₄/Si MIS capacitors, but are in agreement with those of the Si₃N₄/Semi* MIS capacitors, where Semi* is a virtual semiconductor with n_i = 7 × 10¹¹ cm^-3 or E_G = 0.88eV. This indicates that the Si₃N₄/Si/GaAs structure is somewhat like a narrow band gap material with E_G = 0.88eV. The comparison yields strong support for our theoretical energy band of the Si₃N₄/Si/GaAs MIS structure based on quantum well confinement. A depletion mode MIS field-effect-transistor (MISFET) is successfully fabricated with transconductance of 85 mS/mm, and an inversion mode MISFET is fabricated with transconductance of 0.05 mS/mm. The small transconductance for the inversion mode MISFET is ascribed to strong scattering due to confinement of electrons in the Si quantum well.