Modeling of the influence of the contact´s interface on series resistance of high-electron mobility transistor and calculating of microwave performance using HELENA´s software

In order to predict microwave performance of a High-Electron Mobility Transistor (HEMT), the simulator HELENA may be used. This software allows us to calculate the microwave parameters depending on the series resistance of the transistor. To exactly determine the series resistance a way to calculate the value of contact resistance is required. A new approach to evaluate the ohmic contact resistance of the HEMT (based on the AlGaAs-GaAs heterostructure) including the non-uniform interface is presented for the first time. A model is presented where the value of the contact resistance depends on the density of metallic “spikes” at the interface. Regarding the physical parameters of the heterostructure and topology of the designed transistor, we calculated the series resistance in the range between 0.2 to 1.2 Ωmm (in dependence on the processing of the contact). The microwave parameters of the transistor (designed in our laboratory) was calculated using the software HELENA. Results of the simulation confirm the essential influence of contact resistance on the microwave performance