Charge-control modeling of InGaAs/InP heterojunction insulated-gate FETs

A new charge-control model for accumulation-mode heterojunction FETs is presented, This model is used to determine the mobile charge density of the heterojunction channel as a function of the gate voltage. It is the result of a self-consistent combination of semiclassical and quantum-mechanical models. It is shown that the two models can be combined to provide a computationally simple description of the gate control of channel conductivity, and hence gate control of the FET´s I-V characteristics. This merging of two modeling approaches results in a new, easily used, and generalized model with broad applicability to undoped heterostructure devices. A figure of merit called the crossover point, which is the gate voltage at which the sheet charge density in the InP cladding layer is equal to the sheet charge in the 2DEG, is defined. This crossover voltage is found to decrease with increasing InP thickness, which leads to reduced device performance