Development of a silicon ion implantation technology for the aluminum gallium nitride/gallium nitride system.

摘要

AlGaN/GaN high electron mobility transistors (HEMTs) have emerged as the preferred technology for next-generation radar and communications systems because of their exceptional high-power and high-frequency capability. Further improvement in device performance requires minimization of parasitic leakage currents, capacitances and source/drain (S/D) access resistance. In GaN based devices, ion implantation is one of the most promising technologies to reduce the S/D access resistances.;In the past, encapsulant techniques and/or high temperature and custom built high pressure systems were necessary for activation anneal after ion implantation.;In this work, we develop a silicon implantation technology that allows an activation anneal at reduced temperatures in a standard metalorganic chemical vapor deposition (MOCVD) system. Methods are developed that protect the HEMT surface during the activation anneal so that no protective encapsulant is required.;First, the process technology and its effect on the surface morphology and the electrical properties of standard AlGaN/GaN HEMTs are investigated.;Second, the applicability of the process technology for implantation of silicon for ion implanted contacts in the AlGaN/GaN system has been evaluated. To further understand the contact resistances a 3-resistor model for the nonalloyed ion implanted contact was introduced. This model allowed identifying the origin of the relatively high contact resistance initially achieved. Based on this model, device design and implantation conditions were adjusted and state-of-the-art ion implanted contacts were achieved. Finally, the incorporation of Si implantation into AlGaN/GaN HEMTs is demonstrated. After first implementation, efforts are taken to increase the efficiency of those devices. Designs that can increase the transconductance linearity of AlGaN/GaN HEMTs at high current levels are demonstrated.