Minority Carrier Lifetime Of Samples Research Articles

Influence of SiO2 nanosphere on the performance of n+ layer fabricated by phosphorus diffusion using phosphoric acid solution

Phosphorus diffusion was used widely in mass production of p-type silicon solar cells. In order to improve the quality of P doped layer fabricated, a novel phosphorus source mixing phosphoric acid with SiO2 nanosphere was introduced. A high diffusion uniformity of 94.9% was obtained when SiO2 nanosphere was introduced while the uniformity of sample diffused without SiO2 nanosphere was 84.49%. It was found that the formation of dead layer could be avoided by introducing the SiO2 nanosphere, as observed by SEM images, and the minority carrier lifetime of sample was enhanced by 27.87 µs. The surface sheet resistance decreased from 132.62 to 12.8 Ω/□ with the increase of temperature from 825 to 925 °C. Through an etching method, a variation of junction depth increasing from 300 to 571 nm was found with increasing temperature. The variation trends of surface sheet resistance and junction depth with the increase of time were similar with that of temperature.

Control of epitaxial growth at a-Si:H/c-Si heterointerface by the working pressure in PECVD**Project supported by the Natural Science Foundation of Hebei Province, China (Grant No. E2015201203) and the International Society for Theoretical Chemical Physics of China (Grant No. 2015DFE62900).

The epitaxial-Si (epi-Si) growth on the crystalline Si (c-Si) wafer could be tailored by the working pressure in plasma-enhanced chemical vapor deposition (PECVD). It has been systematically confirmed that the epitaxial growth at the hydrogenated amorphous silicon (a-Si:H)/c-Si interface is suppressed at high pressure (hp) and occurs at low pressure (lp). The hp a-Si:H, as a purely amorphous layer, is incorporated in the lp-epi-Si/c-Si interface. We find that: (i) the epitaxial growth can also occur at a-Si:H coated c-Si wafer as long as this amorphous layer is thin enough; (ii) with the increase of the inserted hp layer thickness, lp epi-Si at the interface is suppressed, and the fraction of a-Si:H in the thin films increases and that of c-Si decreases, corresponding to the increasing minority carrier lifetime of the sample. Not only the epitaxial results, but also the quality of the thin films at hp also surpasses that at lp, leading to the longer minority carrier lifetime of the hp sample than the lp one although they have the same amorphous phase.

Recombination of Excess Carriers in Semiconductors

The recombination of excess carriers in semiconductors is discussed on the basis of a model in which the recombination occurs through multiple-levels. The theory is extended to apply to germanium. The dependence of carrier lifetime on temperature in most of pure n -type germanium samples can be explained by introducing two sets of traps, recombination centers ( E C - E r =0.30eV) and hole trapping centers ( E t - E V =0.30eV), in our temperature range. However, the minority carrier lifetime of samples containing comparatively high dislocation density (10 4 –10 5 /cm 2 ) is shown to vary with the dislocation density, and the results is expressed in terms of two lifetimes: τ d , that associated with random dislocations, and τ b , that due to the recombination centers of an undetermined origin. It is also shown that anomalous temperature dependence of the steady-state photoconductivity of high-resistivity p -type nickel doped germanium can be interpreted by assuming that two acceptor levels of nickel atom ar...