Duanlin Que

Grown-in defects in nitrogen-doped Czochralski silicon

Grown-in defects including oxygen precipitates and voids in nitrogen-doped Czochralski (NCZ) silicon have been investigated. It was found that the formation of grown-in oxygen precipitates in NCZ silicon can be divided into two stages. The large precipitates supposed to be enhanced by N2–V2–Ox complexes are generated around 1150 °C, while the small precipitates supposed to be enhanced by NmOn complexes are formed at 750 °C and below. Moreover, it was revealed that the oxygen precipitation behavior in the mixed-type NCZ silicon, which contains vacancy-type and interstitial-type defects distinguished by an OSF-ring in the oxidized wafer, is in sharp contrast to that in the mixed-type Czochralski (CZ) silicon, when subjected to one-step high temperature annealing (1050 °C/32 h) and two-step annealing (800 °C/4 h+1050 °C/16 h). On the other hand, it was found that, compared with CZ silicon, NCZ silicon has much denser crystal originated particles in smaller sizes, which were verified to have been annihilated ...

Texturization of monocrystalline silicon with tribasic sodium phosphate

Abstract Tribasic sodium phosphate (Na 3 PO 4 ·12H 2 O) was successfully introduced to texture monocrystalline silicon for the first time. A series of comparative experiments were made to indicate the dependence of hemispherical surface reflectance on the tribasic sodium phosphate (Na 3 PO 4 ·12H 2 O) concentration, reaction temperature and etching time. Meanwhile, the effects of other agents, such as isopropyl alcohol (IPA), sodium hydroxide (NaOH) and bi-sodium hydrogen phosphate (Na 2 HPO 4 ) on average reflectance were also investigated. The results showed that IPA and NaOH have great detrimental effects on texture, and the average reflectance slightly increased with the addition of Na 2 HPO 4 . On the basis of our experiments, it is concluded that the effect of phosphatidate (PO 4 3− ) or its compounds on the texturization is the same as that of the mixture of alkaline and IPA. Furthermore, this method is economical, has low pollution and good reproducibility. We feel that it is suitable for the large-scale production.

Calculation of critical layer thickness considering thermal strain in Si1−xGex/Si strained-layer heterostructures

In this article, interactions of thermal strain in growth of Si1−xGex strained-layers on Si are analyzed. A formula of critical layer thickness (hc) is obtained based on energy balance considering thermal strain under the assumption that the screw dislocation energy density equals to the sum of the areal strain energy density and thermal strain energy density. The relationship between the thermal expansion coefficient associated with thermal strain and Ge content x is linear. Our calculated values for hc of Si1−xGex strained layers on Si substrates versus mismatch, considering thermal strain, are better agreement with measurements of hc by People and Bean.

Enhancement effect of germanium on oxygen precipitation in Czochralski silicon

Oxygen precipitation in germanium (Ge)-doped Czochralski (CZ) silicon has been investigated through a series of isothermal anneals at temperatures ranging from 550to950°C. It is found that the nucleation of oxygen precipitates can be enhanced in a wide temperature range and the onset temperature for precipitate nucleation can be increased by the germanium doping. Furthermore, it is also revealed that the oxygen precipitates with a higher density and smaller sizes can be formed in germanium-doped CZ silicon in comparison with those in conventional CZ silicon. These two phenomena are ascribed to the reduction in the critical radius for oxygen precipitation and the increase in the concentration of heterogeneous nuclei due to the germanium doping.

The effect of germanium doping on oxygen donors in Czochralski-grown silicon

In this paper the effect of germanium doping on oxygen donors in Czochralski (CZ) silicon has been investigated. It is found that germanium suppresses the formation of thermal donors during annealing at 450??C, as a result of the reaction of Ge with point defects in CZ silicon. Meanwhile, it is clarified that germanium enhances the formation of new donors in CZ silicon, which is proposed to be a process associated with the nucleation enhancement of oxygen precipitation by germanium doping.

Germanium effect on oxygen precipitation in Czochralski silicon

The oxygen precipitation in germanium-doped Czochralski (GCZ) silicon has been investigated. After a prolonged annealing at 800 and 1000°C, it was found that the Ge-doping enhanced the formation of oxygen precipitates with a higher density and modified their morphology and size. Furthermore, the existing oxygen precipitates in the GCZ silicon were readily dissolved, because the Ge-doping facilitated the formation of smaller oxygen precipitates. Based on the facts, the mechanism for the enhancement effect of Ge-doping on oxygen precipitation has been preliminarily discussed.

Texturization of cast multicrystalline silicon for solar cells

The texturization of cast multicrystalline silicon (mc-Si) for solar cells with alkaline or acidic solution has been investigated, and two theoretical models were built on the basis of surface morphologies. For alkaline etching, tilted pyramid structure could be formed on the surface. It is reported that when the tilted angle, which is the angle between (100)-plane and as-cut surface, is larger than the critical angle (20°), the reflectance rapidly increases with the deviation from 100 orientation. For acidic etching, spherical structure was generated. If the ratio, which is the ratio of depth (h) and radius (r) of the spherical structure, is less than the critical value (0.29), the second reflection cannot take place. Therefore, improving the ratio of i and r is one effective way to decrease the reflectance of cast mc-Si, which was proved by subsequent experiment. With the addition of sodium nitrite (NaNO2) or sodium phosphate tribasic (Na3PO4 12H2O) into the acid etchant, it was found that the reflectance decreased remarkably. Finally the formation mechanism of spherical pits in acid etched mc-Si was discussed.

Oxygen precipitation in nitrogen-doped Czochralski silicon

Abstract Oxygen precipitation in nitrogen-doped Czochralski (NCZ) silicon has been investigated by one-step and two-step annealing. It was found that nitrogen in NCZ silicon enhanced oxygen precipitation at lower temperatures (

Intrinsic gettering in germanium-doped Czochralski crystal silicon crystals

Abstract The intrinsic gettering (IG) of germanium-doped Czochralski (GCZ) silicon with different concentrations of germanium has been investigated in this paper. The conventional Czochralski (CZ) and the GCZ silicon samples were annealed using a one-step high temperature process followed by a sequence of low–high temperature annealing cycles. It was found that the good defect-free denude zones in the near surface of the GCZ silicon could be achieved using simply a one-step high temperature annealing process. Furthermore, the density of bulk microdefects as IG sites was higher than that in the CZ silicon, as a result of germanium enhancing oxygen precipitation during three-step annealing. Meanwhile, the experimental results showed that germanium also enhanced the out-diffusion of oxygen. Furthermore, it is believed that germanium doping can increase the ability of IG in CZ silicon wafers.

Enhancement of light-extraction efficiency of SiNx light emitting devices through a rough Ag island film

Based on an ITO/Ag/SiNx/p+-Si/Al structure, a significant enhancement of the external quantum efficiency was achieved compared with the device without Ag island film. Analysis showed that the increase of the light-extraction efficiency resulted from the surface roughening of ITO electrode has a main contribution to this enhancement. The increase of the internal quantum efficiency induced by the enhancement of spontaneous emission rate and the carrier injection level also has an instructive contribution. Our results demonstrate that localized surface plasmons enhanced SiNx-based light emitting devices show great promise for the development of efficiency Si-based optical device.