Gamma Irradiated Diamond Surface and Delta Doped Channel Transistors

David Shahin1, Yizhou Lu1, Aayush Thapa1, Alex Yuan1, Matt Yung1, Kiran Kovi2, James e. Butler2, and A. Christou1
1CALCE, Center for Advanced Life Cycle Engineering, Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20740, USA
2Euclid Techlabs, Cleveland, Ohio, 44139, USA


Diamond transistors with surface 2D conduction channels are projected to be radiation hard with respect to neutrons. However, ionizing radiation hardness may be a problem due to the disruption of the 2D hole concentration. In this paper, the processing of three terminal devices with 2D surface conducting channels is presented as well as analysis of device transfer characteristics. This paper addresses the fabrication, gamma radiation induced defects and device characteristics of field effect transistors (FET) built on 1) high quality diamond surfaces exploiting the 2 dimensional surface conductivity, and 2) the surface two dimensional “hydrogen terminated” conduction layer in diamond single crystals grown by CVD. In particular, the fundamental physics of radiation effects on two dimensional conduction layers in diamond materials is an unexplored area which could lead to new breakthroughs in the performance of high power microwave transistors in extreme environments such as high temperature and high radiation fields. Gamma radiation is shown to be effective in achieving a 2X increase in drain current as well as an increase in drain to source saturation current and transconductance. The results are compared to GaN enhancement mode FETS which show a significant degradation of transconductance.

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