Capacitance-voltage characteristics of a Schottky junction containing SiGe/Si quantum wells

The capacitance-voltage (C-V) characteristics of SiGe/Si quantum wells located near or in the space-charge region of a Schottky barrier have been numerically simulated by solving the Poisson equation. A physical picture of the variations of energy band and charge density in the quantum-well structure under the bias voltage is presented. The predominant feature of the C-V curves of quantum-well structures is the appearance of a capacitance plateau for single quantum wells or a series of plateaus for multiple-quantum-well samples. From the coincidence between the measured C-V curve and the simulated one, the band offset at the heterointerface could be derived. Moreover, the structural parameters of the quantum-well sample could be obtained from the measured C-V curves. It is found that the carrier-concentration profile derived from the C-V curve by the ordinary differential method does not coincide with the real carrier distribution in the quantum well; only the peak height of the C-V carrier concentration profile is related to the average carrier concentration in the well.