Investigation of high resistivity p-type FZ silicon diodes after 60Co {\gamma}-irradiation

TL;DR

This study examines how high resistivity p-type FZ silicon diodes respond to gamma irradiation, analyzing both macroscopic electrical properties and microscopic defect formations, including their thermal stability and surface conductance changes.

Contribution

It provides new insights into defect evolution and stability in high resistivity p-type FZ silicon diodes under gamma irradiation, with detailed microscopic and macroscopic characterization.

Findings

Radiation induces specific defect complexes like B$_i$O$_i$ and C$_i$O$_i$ in the silicon diodes.

High dose irradiation affects surface conductance and causes unexpected changes in capacitance-voltage measurements.

Thermal annealing influences defect stability and surface properties, revealing complex defect dynamics.

Abstract

In this work, the effects of $^\text{60}$Co $\gamma$-ray irradiation on high resistivity $p$-type diodes have been investigated. The diodes were exposed to dose values of 0.1, 0.2, 1, and \SI{2}{\mega Gy}. Both macroscopic ($I$--$V$, $C$--$V$) and microscopic (Thermally Stimulated Current~(TSC)) measurements were conducted to characterize the radiation-induced changes. The investigated diodes were manufactured on high resistivity $p$-type Float Zone (FZ) silicon and were further classified into two types based on the isolation technique between the pad and guard ring: $p$-stop and $p$-spray. After irradiation, the macroscopic results of current-voltage and capacitance-voltage measurements were obtained and compared with existing literature data. Additionally, the microscopic measurements focused on the development of the concentration of different radiation-induced defects, including the boron interstitial and oxygen interstitial (B$_\text{i}$O$_\text{i}$) complex, the carbon interstitial and oxygen interstitial C$_\text{i}$O$_\text{i}$ defect, the H40K, and the so-called I$_\text{P}^*$. To investigate the thermal stability of induced defects in the bulk, isochronal annealing studies were performed in the temperature range of \SI{80}{\celsius} to \SI{300}{\celsius}. These annealing processes were carried out on diodes irradiated with doses of 1 and \SI{2}{\mega Gy} and the corresponding TSC spectra were analysed. Furthermore, in order to investigate the unexpected results observed in the $C$-$V$ measurements after irradiation with high dose values, the surface conductance between the pad and guard ring was measured as a function of both dose and annealing temperature.