6. GD-MOSFET Structure

In the previous chapter, it was demonstrated that the specific on-resistance for power MOSFET structures can be greatly reduced by utilizing the two-dimensional charge-coupling concept. In these structures, a uniform doping concentration was assumed for the drift region. Although the electric field profile in this case is superior to that observed for a one-dimensional junction, the electric field was found to be non-uniform through the drift region. This non-uniformity of the electric field is relatively small for devices with low (∼30 V) blocking voltage capability. However, when the desired blocking voltage is large (60–200 V), the electric field varies exponentially with distance in the uniformly doped drift region resulting in a low electric field through a large portion of the distance between the drain and source regions.