100 MeV Si7+ Ion Irradiation Induced Modifications in Electrical Characteristics of Si Photo Detector: An In-Situ Reliability Study

Shammi Verma,V Shobha,D Kanjilal,B Jayashree,M Vinay Kumar,S Krishnaveni,Ramani Ramani

doi:10.5539/jmsr.v3n3p24

Abstract

The influence of 100 MeV Silicon (Si) ion irradiation on electrical characteristics of Si photo detectors has been analyzed using in-situ current-voltage characterization (I-V) in dark condition. The irradiation was performed over a wide range of fluences from 1×1011 ions/cm2 to 1×1013 ions/cm2. Key electrical parameters such as ideality factor (n), series resistance (Rs) and reverse bias leakage current (IR) for each irradiation fluence have been extracted from the I-V characteristics. The ideality factor of the unirradiated detector is found to be 1.48 and it gradually increased up to the fluence of 5×1011 ions/cm2, then it saturates around 3.4-3.5 for higher fluences. The I-V characteristics showed significant increase in forward bias and drastic increase in reverse leakage current. The value of IR is 7.23 nA for unirradiated detector and it increases about four orders of magnitude up to 5×1011 ions/cm2. Further there is no observable change in the value of IR. However the value of Rs increases initially and slightly decrease at higher fluences. The observed results are interpreted in terms of energy loss mechanisms of swift heavy ion as it passes through the different layers of the detector. The radiation induced defects in the bulk region and activation of multiple current transport mechanisms have attributed to the observed deviations in the electrical behaviour of the device. SRIM (Stopping power and Range of Ion in Matter) and TRIM (Transport and Range of Ion in Matter) simulation results of damage induced in the device have been reported in the present study. Linear energy transfer (LET), non ionizing energy loss (NIEL) damage contributions, total ionization dose (TID) and displacement damage dose (Dd) has been correlated with the observed degradation. Quantitative estimation of radiation hardness of the Si photo detector is done by comparing with the equivalent damage created by the proton at similar penetration depth in the present device structure.

Highlights

The Si Photo detectors are major part of several electro-optical instruments used in space and military applications
In the present study we have used SRIM 2013 program to study the passage of 100 MeV Si ion beam through the Si photo detector
The non ionizing energy loss (NIEL) induced displacement damage appears to be the major effect to the observed degradation primarily in the bulk region of the device

Summary

Introduction

The Si Photo detectors are major part of several electro-optical instruments used in space and military applications These are being used extensively for energy and position measurements in particle and nuclear physics experiments (Kurokawa et al, 1995). In such experiments the detectors are exposed to typically 100 Mrad in their operational lifetime (Gill, Hall, & MacEvoy, 1997). The effect of swift heavy ion (SHI) on photo detectors, high energy heavy ion has not been reported extensively It is well documented in the literature that SHI irradiation in semiconductors can create latent tracks, induce modifications such as vacancies, di-vacancies, point defects etc (Bolse & Beate, 2002; Levalois & Marie, 1999; Kanjilal, 2001). LET is the sum of electronic and nuclear energy losses and plays an important role in case of heavy ions

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