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The greater the positive charge placed on the gate, the more positive the applied gate voltage, and the more holes that leave the semiconductor surface, enlarging the depletion region. (In this device there is a limit to how wide the depletion width may become.
In the semiconductor at the smaller voltage shown in the top panel, the positive charge placed on the left face of the insulator lowers the energy of the valence band edge. Consequently, these states are fully occupied out to a so-called depletion depth where the bulk occupancy reestablishes itself because the field cannot penetrate further.
More specifically, over time positive charges become trapped at the oxide-semiconductor boundary underneath the gate of a MOSFET. These positive charges partially cancel the negative gate voltage without contributing to conduction through the channel as electron holes in the semiconductor are supposed to. When the gate voltage is removed, the ...
This gate permits electrons to flow through or blocks their passage by creating or eliminating a channel between the source and drain. Electron-flow from the source terminal towards the drain terminal is influenced by an applied voltage. The body simply refers to the bulk of the semiconductor in which the gate, source and drain lie.
When a negative gate-source voltage (positive source-gate) is applied, it creates a p-channel at the surface of the n region, analogous to the n-channel case, but with opposite polarities of charges and voltages. The increase in hole density corresponds to increase in capacitance, shown in the left part of right figure.
Like the floating gate memory cell, a charge trapping cell uses a variable charge between the control gate and the channel to change the threshold voltage of the transistor. The mechanisms to modify this charge are relatively similar between the floating gate and the charge trap, and the read mechanisms are also very similar.
A positive V GS attracts free-floating electrons within the body towards the gate. But enough electrons must be attracted near the gate to counter the dopant ions and form a conductive channel. This process is called inversion. The conductive channel connects from source to drain at the FET's threshold voltage.
A schematic of a MISFET is shown in Figure 1a. The source and the drain are connected by a semiconductor and the gate is separated from the channel by a layer of insulator. If there is no bias (potential difference) applied on the gate, the Band bending is induced due to the energy difference of metal conducting band and the semiconductor Fermi ...