A physics-based heterojunction bipolar transistor model for integrated circuit simulation

A new physics-based dc model for a heterojunction bipolar transistor (HBT) has been developed. This model offers features not found in previous analytical or physics-based HBT models, such as consideration of a cylindrical emitter-base geometry and direct implementation into SPICE (Simulation Program with Integrated Circuit Emphasis). The model parameters are determined from a knowledge of the device material, geometry, and fabrication process. The HBT model is developed by using semiconductor physics to calculate modified parameters for the existing SPICE Bipolar junction transistor (BJT) model. Model generated data was obtained via a SPICE dc simulation for devices with different geometries and doping profiles. The resulting current-voltage characteristics were compared to the corresponding measured curves and excellent agreement was, obtained. The model predicted the device´s performance over its entire dc range of operation to within ±5%. Although a few of the model parameters were determined empirically, the physical nature of the model provides insight into new device designs by directly relating the material, geometry, and process specifications to the model parameters