Capacitance modulation from submicron domain on ferroelectric-semiconductor media

Reproduction capacitance signal of a ferroelectric-semiconductor disk memory was studied by numerical simulation under an extremely high-density recording condition. Information is recorded by controlling the direction of the ferroelectric polarization which induces the change of depletion-capacitance of the semiconductor substrate. When the spatial wavelength is less than 1 µm, depletion regions connect with each other, which is called the “punch-through” effect. It has been considered that the depletion-capacitance modulation disappears in the “punch-through” state. The present numerical simulation, however, suggested that for the ferroelectric-semiconductor structure, the modulation signal of depletion-capacitance does not disappear even in the “punch-through” state, because there exist island accumulation regions at the semiconductor surface due to the ferroelectric polarization of domains with opposite direction. This result is consistent with previous experimental results. It is suggested that the ferroelectric-semiconductor disk memory has a potential for higher density recording than silicon nitride-silicon disk memories.