A study of thermal stability of different ZnO/p-Si diode structure toward application of radiation detectors

Abstract

Radiation hard detectors are difficult and costly to design. Moreover silicon based detectors are not superior in-term of high temperature environment compared to wide band semiconductor materials such as zinc oxide (ZnO). ZnO semiconductor are actively studied for the past decade due to its versatile properties such as high transparency, ability to be deposited at low temperatures, and high resistance towards radiation. Radiation hard materials must be able to withstand high temperature operation. A nuclear power plant demands high temperature up to 673 K operation especially near reactor pressure vessel. Not many work are done on the effect of temperature on radiation hard semiconductor material. The aims of this research is to remodel and simulating two different ZnO/p-Si heterojunction diode structure material and to study the temperature effect of diode parameters such as barrier height, apparent barrier height, ideality factor (n), series resistance, shunt resistance, simulation of Spice ZnO/p-Si heterojunction diode model and subsequently to optimize thermal stability for high temperature application such as radiation detector and electrical power plant. Modeling and simulation was analyzed and executed in Matlab and LTSpice. During characterization, the temperature were ramped-up from room temperature to 673 K. Furthermore, this analyzed result were compared to experimental result that have been published on high ranking journal. For each temperature, the parameters extracted were tabulated. Subsequently, all electrical characteristic obtained have been plotted on graph. On top of that, the effect of barrier inhomogeneity have been carried out and there were three prime prove of barrier inhomogeneity which is small barrier height value obtain from gradient of l n ( T .) versus V-1 , low Richardson constant value, and linearly lines on plotted barrier height against ideality factor. Result shows the structure 1 ideality factor of 2.07 were achieved at 673 K temperature with semi-empirical structure 2 hole concentration and calculated structure 1 electron concentration of 7.05x106cm-3 and 2.59x1013cm-3 respectively. Beside that, the activation energy was found at 0.35 eV. In conclusion, structure 1 ZnO/p-Si heterojunction diode shows good thermal stability compared to structure 2 but structure 2 show ability to fabricate high current and low turn on voltage of 0.8 V at room temperature. It has been observed that structure 1 ZnO/p-Si can withstand up to 673 K temperature thus proven that ZnO/p-Si as an substitute or alternative to high temperature environment operation.