Modeling and Electrical Characterization of Ohmic Contacts on n-type GaN

As the current requirements of power devices are moving towards high frequency, high efficiency and high-power density, Silicon-based devices are reaching its limits which are instigating the need to move towards new materials. Gallium Nitride (GaN) has the potential to meet the growing demands due to the wide band-gap nature which leads to various enhanced material properties like, higher operational temperature, smaller dimensions, faster operation and efficient performance. The metal contacts on semiconductors are essential as the interface properties affect the semiconductor performance and device operation. The low resistance ohmic contacts for n-GaN have been well established while most p-GaN devices have still high contact resistivity. Significant work has not been found that focuses on software-based modeling of the device to analyze the contact resistance and implement methods to reduce the contact resistivity. Understanding the interface physics in n-GaN devices using simulations can help in understanding the contacts on p-GaN and eventually reduce its metal contact resistivity.

In this work, modeling of the metal-semiconductor interface along with the effect of a heavily doped layer under the metal contact is presented. The extent of reduction in contact resistivity due to different doping and thickness of n++ layer is presented with simulations. These results have been verified by the growth of device based on simulation results and reduction in contact resistivity has been observed. The effect of different TLM pattern along with different annealing conditions is presented in the work.