Compact Modeling of High-Voltage (LDMOS/MISHEMT) Devices
(August 6, 2007 -- March 28, 2012)
In this thesis, physics-based analytical compact models are developed for the laterally diffused metal-oxide-semiconductor (LDMOS) transistor and the metal-insulator-semiconductor high electron mobility transistor (MISHEMT), respectively, in order to aid the microwave circuit simulation. The LDMOS is physically divided into two regions: the core channel and the drift channel. Surface potential based drain current models are developed for the core channel and the drift channel individually. Then a sub-circuit that consists of the core channel and the drift channel is used to model the current voltage characteristic of the LDMOS. Due to the lateral nonuniform doping in the core channel, there are peaks in the capacitances of the LDMOS. The “peaky” capacitances cannot be captured by the charge model formulated based on the Ward-Dutton (WD) partition scheme. In this regard, a new charge partition method that is applicable in the presence of lateral non-uniform doping is proposed. Based on the proposed method, for the first time, a compact charge model that is able to reproduce the peaky capacitance is derived. MISHEMT’s operation is based on the conduction of the 2-dimensional-electron-gas (2DEG). A physical and explicit expression for the 2DEG density considering two lowest subbands, which is valid from subthreshold region to the active operation region, is derived for the first time. With the newly derived 2DEG density expression, an analytical and symmetrical drain current model for the MISHEMT is formulated based on the bulk MOS current model.
Original Title: Compact Modeling of Non-classical MOSFETs