Bistability of the BiOi complex and its implications on evaluating the “acceptor removal” process in p-type silicon

Abstract

The dependencies of the BiOi defect concentration on doping, irradiation fluence and particle type in p-type silicon diodes have been investigated. We evidenced that large data scattering occurs for fluences above 10 12 1 MeV neutrons/cm 2 , becoming significant larger for higher fluences. We show that the BiOi defect is metastable, with two configurations A and B, of which only A is detected by Deep Level Transient Spectroscopy and Thermally Stimulated Currents techniques. The defect' electrical activity is influenced by the inherent variations in ambient and procedural experimental conditions, resulting not only in a large scattering of the results coming from the same type of measurement but making any correlation between different types of experiments difficult. It is evidenced that the variations in [BiOi A ] are triggered by subjecting the samples to an excess of carriers, by either heating or an inherent short exposure to ambient light when manipulating the samples prior to experiments. It causes ~7h variations in both, the [BiOi A ] and in the effective space charge. The analyses of structural damage in a diode irradiated with 10 19 1 MeV neutrons/cm 2 revealed that the Si structure remains crystalline and vacancies and interstitials organize in parallel tracks normal to the Si-SiO2 interface.

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

“…The changes in Ge content perturb the ratio of the B-Si and Si-B-Ge states within crystal bulk and thereby local strain and density of N S . This might be a reason for the metastability of B i O i complexes, which appeared in two configurations of [B i O i A ] and [B i O i B ] [ 2 , 3 ]. Additionally, it had been concluded [ 31 ] that most of the strain in SiGe is accommodated by variations of both the bond angle and bond length.…”

“…The minority carrier trap E1 with activation energy of 0.150 ± 0.005 eV can be associated with a vacancy–oxygen complex (VO) [ 5 ]. The electron trap E2 characterized by activation energy of 0.240 ± 0.005 eV can be ascribed to the interstitial boron–interstitial oxygen complex (B i O i ) [ 2 , 5 , 18 ]. The MCT spectra recorded after IR illumination and followed retention in dark for 16 h showed that the B i O i complex is in a stable state B i O i A of maximum concentration.…”

“…The radiation-induced boron dopant transformations in p -type Si lead to the so-called effect of “acceptor removal” [ 1 , 2 , 3 , 4 , 5 ], which degrades the performance of particle detectors. This happens due to the substitutional lattice site boron (B s ) transformation into interstitial (B i ) boron under irradiation.…”

“…The change of this state can be modified by illumination, temperature jump or applied external electrical field, where the transformations are mediated by electron–phonon interaction [ 6 ]. The B i O i complex in Si is also a metastable defect existing in at least two configurations, namely [B i O i A ] and [B i O i B ] [ 2 , 3 ]. The density of the [B i O i A ] configuration complexes is usually reduced under external perturbation using light or temperature (heating to 353 K) due to their transformations to [B i O i B ] state [ 3 ].…”

“…The density of the [B i O i A ] configuration complexes is usually reduced under external perturbation using light or temperature (heating to 353 K) due to their transformations to [B i O i B ] state [ 3 ]. However, the maximum concentration of [B i O i A ] can then be restored [ 2 , 3 ] by retention in dark at reduced temperatures [ 3 ]. It has been reported [ 8 , 9 , 10 ] that silicon–germanium (Si 1−x Ge x ) alloys are promising for the production of detectors operational in radiation harsh environments.…”