FOXFET STRUCTURE - DEVICE MODELING AND ANALYSIS

A FOXFET structure for biasing AC coupled detector structures has been analyzed by a two-dimensional device simulation. For this purpose, a floating strip junction with zero current boundary condition has been applied. The floating strip voltage increase is analyzed from depletio n layer spreading through three charge regions: electron accumulation surface region, hole current flow region and depleted bulk region. As a result, the floating strip potential increases approximately as the square root of the drain/backside reverse voltage. Strip potential sat uration is observed for oxide charge densities larger than 5 x 10(11) cm(-2) and results in a weaker gate control and oxide thickness influe nce. Current conduction mechanisms are critically discussed and drift- diffusion injection from the floating strip junction is proposed inste ad of the thermionic emission model. Strip potential increase by an ad ditionally injected strip current is due to the effect of space-charge -limited-current (SCLC) for an injected strip current larger than appr oximately 10(-9) A/mu m. The dynamic resistance calculated from numeri cally obtained strip current/voltage curves has a slope of 0.85 for a lower injected strip current (I-S < 10(-10) A/(mu m) and decreases to 0.6 for a larger one.