5.5 MeV Electron Irradiation-Induced Transformation of Minority Carrier Traps in p-Type Si and Si1−xGex Alloys

Jevgenij Pavlov,Eugenijus Gaubas,Tomas Ceponis,Leonid Makarenko,Kornelijus Pukas

doi:10.3390/ma15051861

Abstract

Minority carrier traps play an important role in the performance and radiation hardness of the radiation detectors operating in a harsh environment of particle accelerators, such as the up-graded sensors of the high-luminosity hadron collider (HL-HC) at CERN. It is anticipated that the sensors of the upgraded strip tracker will be based on the p-type silicon doped with boron. In this work, minority carrier traps in p-type silicon (Si) and silicon–germanium (Si1−xGex) alloys induced by 5.5 MeV electron irradiation were investigated by combining various modes of deep-level transient spectroscopy (DLTS) and pulsed technique of barrier evaluation using linearly increasing voltage (BELIV). These investigations were addressed to reveal the dominant radiation defects, the dopant activity transforms under local strain, as well as reactions with interstitial impurities and mechanisms of acceptor removal in p-type silicon (Si) and silicon–germanium (SiGe) alloys, in order to ground technological ways for radiation hardening of the advanced particle detectors. The prevailing defects of interstitial boron–oxygen (BiOi) and the vacancy–oxygen (VO) complexes, as well as the vacancy clusters, were identified using the values of activation energy reported in the literature. The activation energy shift of the radiation-induced traps with content of Ge was clarified in all the examined types of Si1−xGex (with x= 0–0.05) materials.

Highlights

Academic Editor: Wen-Tong GengThe radiation-induced boron dopant transformations in p-type Si lead to the so-called effect of “acceptor removal” [1–5], which degrades the performance of particle detectors.This happens due to the substitutional lattice site boron (Bs ) transformation into interstitial (Bi ) boron under irradiation
Further migration of this Bi dopant and its reaction with interstitial oxygen impurity (Oi ) in silicon crystal determines the formation of the interstitial boron–interstitial oxygen complex (Bi Oi )
[Bi Oi A ] can be restored [2,3] by retention in dark at reduced temperatures [3]. It has been reported [8–10] that silicon–germanium (Si1−x Gex ) alloys are promising for the production of detectors operational in radiation harsh environments

Summary

Introduction

The radiation-induced boron dopant transformations in p-type Si lead to the so-called effect of “acceptor removal” [1–5], which degrades the performance of particle detectors. This happens due to the substitutional lattice site boron (Bs ) transformation into interstitial (Bi ) boron under irradiation. [Bi Oi A ] can be restored [2,3] by retention in dark at reduced temperatures [3] It has been reported [8–10] that silicon–germanium (Si1−x Gex ) alloys are promising for the production of detectors operational in radiation harsh environments. The spectrum of deep traps of majority carriers in p-type Si and SiGe alloys, the metastability of the carbon–oxygen complexes and shifts of the activation energy of these defects were investigated in our previous article [7]. It was shown that shifts of activation energy of the minority carrier traps appear due to an increase in Ge content in SiGe alloys

Samples and Measurement Techniques

Recorded Characteristics and Extracted Parameters

Findings

Discussion

MeV electron-irradiated p-type