Electron-irradiation-induced defects in Si-Ge alloys

Goubet, J. J.; Stiévenard, D.; Mathiot, D.; Zazoui, M.

doi:10.1103/physrevb.46.10113

Cited by 26 publications

(8 citation statements)

References 33 publications

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“…10,12 However, the energy level of this transition lies close to or below the midgap at high Ge contents like the ones in this study. 21 Therefore, this transition cannot be the one we observe here, since the vacancies in the annealed samples with 10% of Ge and a P concentration of 10 18 cm −3 clearly are in a negative charge state in the temperature interval of 200-300 K.…”

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confidence: 71%

Evidence of a second acceptor state of theEcenter inSi1−xGex

2007

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We have found evidence of a second acceptor state of the E center in Si 1−x Ge x by using positron annihilation spectroscopy. To achieve this, we studied proton irradiated n-type Si 1−x Ge x with a Ge content of 10%-30% and a P dopant concentration of 10 18 cm −3 , in which the number of Ge atoms around irradiation induced E centers was increased by annealing. When measuring the Doppler broadening of the annihilation line, the shape parameter S starts to decreases at 150 K with decreasing measurement temperature. This indicates that a charge transition in the upper half of the Si 1−x Ge x band gap, above the well known ͑0/Ϫ͒ level, takes place. Hence, we suggest that the increased concentration of germanium around the E center pulls down the localized second acceptor state into the Si 1−x Ge x band gap, making the Ge decorated E center a more effective trap for conduction electrons.

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confidence: 71%

Evidence of a second acceptor state of theEcenter inSi1−xGex

2007

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“…Recent developments on the V-O, V 2 , V-P, and V-Sb centers have been reported in Si 1−x Ge x alloys. [10][11][12][13][14] Most of these studies were done either on fully strained ͑ =0͒ or fully relaxed ͑ = 100% ͒ Si 1−x Ge x , where is the degree of strain relaxation. In a recent deeplevel transient spectroscopy ͑DLTS͒ study, 10 a defect labeled E1 is observed in phosphorous ͑P-͒doped fully strained Si 1−x Ge x alloys grown by chemical vapor deposition ͑CVD͒ and was tentatively attributed to V-P pair.…”

Section: Introductionmentioning

confidence: 99%

Deep-level transient spectroscopy study of theEcenter inn−Siand partially relaxedn−
Mamor
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Elzain
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Bouziane
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et al. 2008
Phys. Rev. B
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We have employed deep-level transient spectroscopy to investigate the electronic properties of defects introduced during high energy He-ion irradiation of epitaxially grown phosphorous-doped n-Si and partially relaxed n-Si 0.9 Ge 0.1 . It is found that He-ion irradiation introduces two major defects in Si and Si 0.9 Ge 0.1 . These have been attributed to a doubly negative charge state of the divacancy ͑V 2 =/− ͒ and V-P pair ͑E center͒. The germanium dependence of the activation enthalpy ͑E H ͒ for both ͑V 2 =/− ͒ and V-P pair is found to be relatively minute with a small decrease and increase in the corresponding E H with respect to that of Si, respectively. Comparison was made with earlier reported results in phosphorous-doped fully strained n-Si 1−x Ge x and antimony-doped totally relaxed n-Si 1−x Ge x layers to directly assess the influence of strain relaxation on radiation-related deep levels in Si 1−x Ge x . It is shown that the energy level of the V-P pair in fully strained and partially relaxed Si 1−x Ge x lies closely to that reported for V-Sb in fully relaxed Si 1−x Ge x . This result indicates that the V-P level is independent of strain, suggesting that such defect is pinned to the conduction band. Moreover, our calculation using full-potential linearized augmented plane wave method shows nonpreferential site occupancy of the phosphorous relative to Ge atoms. This implies a chemical disorder in the vicinity of the V-P center which leads to a fluctuation of the ionization energy level of the E center. This fluctuation is associated with a distribution of the electron emission rate between the V-P level and the conduction band edge.

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“…For the samples annealed under 400¨600 -C ambient, the point defects could be annealed out, releasing electrons, and thus holes are compensated, leading to higher ohmic contact resistance. The behavior of defects induced by plasma or electron bombardment has been widely observed in compound semiconductor, such as GaN [17,18] and SiGe [19,20]. The sample annealed under 500 -C showed lower ohmic contact resistance than the one under 400 -C. It might be explained by the point defects reactivated under 500 -C annealing temperature, causing an increase of hole concentration and hence the contact resistance was reduced.…”

Section: Resultsmentioning

confidence: 92%