Yttrium passivation of defects in GeO2 and GeO2/Ge interfaces

Li, Hongfei; Robertson, John

doi:10.1063/1.4974291

Cited by 12 publications

(3 citation statements)

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“…On the other hand, the experimental results of almost no dependency on Al 2 O 3 thickness and the meaningful dependency of GeO x thickness on ΔN st in the Al 2 O 3 /GeO x /p-Ge gate stacks indicate that hole slow traps exist near the Al 2 O 3 /GeO x interface, as shown in Figure 5b. The energy positions of these possible slow traps seem consistent with the calculated defect energy levels in Al 2 O 3 and GeO 2 , 32,33 which are also shown in Figure 5. First, the calculated four energy levels of defects in Al 2 O 3 are corresponding to those of oxygen vacancies in Al 2 O 3 .…”

Section: Resultssupporting

confidence: 86%

“…Also, the calculated two energy levels of defects in GeO 2 are corresponding to those of valence alternation pair (VAP) defects in GeO 2 . 33 The energy level of the higher one, located close to the conduction band minimum of Ge, is consistent with the energy level of the slow traps for electrons and, thus, can be a possible physical origin of the slow trap for electrons.…”

Section: Resultssupporting

confidence: 73%

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Slow Trap Properties and Generation in Al₂O₃/GeO_x/Ge MOS Interfaces Formed by Plasma Oxidation Process

Takenaka

Takagi

2019

ACS Appl. Electron. Mater.

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For realizing Ge CMOS devices with a small equivalent oxide thickness (EOT) and a low density of fast interface states (D it), understanding of slow traps in Ge gate stacks and reduction of its density are one of the most crucial issues. For this purpose, we examine slow trap density and locations of Al2O3/GeO x /Ge MOS gate stacks, which are fabricated by plasma oxidation in this work. In Al2O3/GeO x /Ge MOS interfaces formed by preplasma oxidation (pre-PO) and postplasma oxidation (post-PO), slow trap density has been compared. Also, the slow trap density on the thickness dependence of GeO x and Al2O3 is systematically evaluated for the Al2O3/GeO x /Ge MOS gate stacks formed by pre-PO. It is found that near the conduction band edge of Ge, additional electron slow traps will be generated by using the post-PO process. Above all, in the Al2O3/GeO x /Ge MOS interfaces with pre-PO. The main slow traps can be located near the GeO x /Ge interfaces for the electrons and the Al2O3/GeO x interfaces for the holes, respectively.

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Section: Resultssupporting

confidence: 86%

Section: Resultssupporting

confidence: 73%

Slow Trap Properties and Generation in Al₂O₃/GeO_x/Ge MOS Interfaces Formed by Plasma Oxidation Process

Takenaka

Takagi

2019

ACS Appl. Electron. Mater.

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“…This consists of a positively charged 3-fold O site, and a negatively charged 3-fold Ge site. These sites have been seen in simulations of a-GeO 2 and a-SiO 2 [29,30]. Briefly, they are O-deficiency defects created from O vacancies.…”

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confidence: 94%

Germanium oxidation occurs by diffusion of oxygen network interstitials

Robertson

2017

Applied Physics Letters

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Density functional modeling is used to show that germanium oxidation occurs by the diffusion of network oxygens across the film as peroxyl bridges, not by molecular O 2 interstitials (O 2 *). The smaller O bond angle of GeO 2 leads to lower order rings in the amorphous GeO 2 network than in SiO 2 . This leads to narrower interstitial diffusion channels, and less dilation of the interstitial volume around the transition state. This raises the migration barrier of O 2 * in GeO 2 , so that the overall diffusion energy of O 2 * in GeO 2 is now higher than that of a network O interstitial. The low formation energy of the O vacancy in GeO 2 leads to GeO 2 being O-poor very near the Ge/GeO 2 interface, but the lower overall diffusion energy of the O network interstitial than the vacancy leads to the network interstitial dominating diffusion.Silicon has been the dominant semiconductor for many years largely because SiO 2 is such a well-behaved oxide. However, to continue Moore's law scaling, it is becoming necessary to replace Si with a higher mobility semiconductor. Ge has higher electron and hole mobilities than Si and would be a reasonable choice. However, Ge has a poor native oxide GeO 2 with a poorer interface with its parent Ge for reasons that are not fully understood [1-3].Historically, one of the notable features of silicon was its well-understood oxidation process. Silicon oxidation follows the linear/quadratic Deal-Grove model [4], in which the O 2 molecule diffuses along interstitial channels of the amorphous (a-) SiO 2 network [4,5], to react exothermically with Si at the Si/SiO 2 interface [6][7][8][9]. This occurs because of the remarkably open network of a-SiO 2 . This model was verified by the lack of O isotopic exchange with the existing network oxygens [10,11]. Ge oxidation somehow differs, it creates Ge/GeO 2 interfaces with more interfacial defects [1,2], molecular GeO is volatile [12], the oxidation kinetics follow an unusual pressure dependence [13], but the Ge/GeO 2 interface can be flat [14]. Here, we analyze the Ge oxidation mechanism in terms of atomic transport processes across the GeO 2 layer, and conclude that it occurs mainly by transport of oxygen network interstitials (also known as peroxyl bridges) rather than by molecular oxygen interstitials [15]. A hint of this is already seen by comparing the experimental oxidation rates of Si and Ge [5,12,13], and the kinematic viscosities of SiO 2 and GeO 2 [16][17][18][19] in Fig 1(a).

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Varying internal parameters in the thermal silicon oxidation

Maser

2019

J Solid State Electrochem

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Yttrium passivation of defects in GeO2 and GeO2/Ge interfaces

Cited by 12 publications

References 33 publications

Slow Trap Properties and Generation in Al₂O₃/GeO_x/Ge MOS Interfaces Formed by Plasma Oxidation Process

Slow Trap Properties and Generation in Al₂O₃/GeO_x/Ge MOS Interfaces Formed by Plasma Oxidation Process

Germanium oxidation occurs by diffusion of oxygen network interstitials

Varying internal parameters in the thermal silicon oxidation

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Yttrium passivation of defects in GeO2 and GeO2/Ge interfaces

Cited by 12 publications

References 33 publications

Slow Trap Properties and Generation in Al2O3/GeOx/Ge MOS Interfaces Formed by Plasma Oxidation Process

Slow Trap Properties and Generation in Al2O3/GeOx/Ge MOS Interfaces Formed by Plasma Oxidation Process

Germanium oxidation occurs by diffusion of oxygen network interstitials

Varying internal parameters in the thermal silicon oxidation

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Slow Trap Properties and Generation in Al₂O₃/GeO_x/Ge MOS Interfaces Formed by Plasma Oxidation Process

Slow Trap Properties and Generation in Al₂O₃/GeO_x/Ge MOS Interfaces Formed by Plasma Oxidation Process