Influence of “gate-biasing effect” on BSIT´s saturated property

For BSIT, it is well-known that the ideal relation between the drain current and the drain voltage with respect to the source is pentode-like, the saturated property. But the result from practical measurements shows I_D increases slightly with rising V_D , just like the phenomenon observed in a BJT, which is affected by “base width modulation”. The authors deduce that the main cause is “gate-biasing effect”. In this article, the effect is discussed in detail