We present a theory of the low-temperature transport of holes confined in the Ge strained channel of single-side modulation-doped SiGe/Ge/SiGe square quantum wells (QWs). Besides the well-known scattering mechanisms such as remote impurities and surface roughness, the theory includes misfit deformation potential. We prove that due to the effect from doping-induced band bending, the surface roughness and misfit deformation potential scatterings are considerably strengthened. Accordingly, these are found to be the key scattering mechanisms in the SiGe/Ge/SiGe system, which are still a subject under debate. Our theory can explain all recent experimental data about the transport properties of interest, namely, the carrier-density dependences of the hole mobility and the ratio of the transport to quantum lifetimes. Further, the calculated hole mobility in Ge strained QWs exhibits a special channel-width dependence with a sharp peak, which was observed but has not been explained so far.
This study aims to assess the pollution level of groundwater in the Holocene aquifer in the Duy Tien district, Ha Nam province, using the groundwater quality index (GWQI). Groundwater samples were collected from 20 wells and dug wells in households in rainy and dry seasons. The results showed that many parameters such as ammonium, nitrite, total hardness, chloride, Fe, Mn, Pb, As exceeded the permitted limits according to QCVN 09-MT: 2015/BTNMT. In particular, the ammonium concentrations at all monitoring wells were higher 2,73 ÷ 28,3 times than permitted values. The GWQI ranged between 84 ÷ 369 in the rainy season and 67 ÷ 290 in the dry season, while the proportion of wells with "very poor water" quality in the rainy and dry season was 50% and 65%, respectively. The GWQI values can be a scientific basis for effective use and protecting groundwater resources.
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