Ionized impurity scattering mobility

Fig.tr.1-123 InN. Electron mobility vs. temperature for three samples with RT carrier concentrations of 5.3 X IQi (1), 7.5 X 10 6 (2), and 1.8x 10 cm (3). Left broken line, calculated ionized-impurity-scattering mobility right broken line, empirical high-temperature mobility jjL (X T ) for sample 1. Solid lines, total mobdity calculated for each sample [1.109]... 

The maxima of the mobilities around 50-100 K are caused by the onset of ionized impurity scattering. The highest measured mobility at about 80 K is... 

Fig. 2.5. Temperature-dependent mobility of ZnO single crystals measured with the current flowing parallel (a) or perpendicular (b) to the c-axis of the crystals. The theoretical mobilities for the different scattering processes (optical, acoustical, and piezoelectric as well as ionized impurity scattering) as calculated by Wagner and Helbig [34,35] are shown as differently dashed lines. The calculated combined mobility curves (solid lines) fit the experimental data quite well for temperatures above about 20-50 K. The carrier concentrations at 300 K were about Ad — Na = 2.25 x 1016 cm 3 and Na = 2.75 x 1016 cm 3 (compensation ratio Aa/Ad = 0.55)...

Fig. 2.8. (a) Hall mobility as a function of the temperature for an undoped epitaxial ZnO layer and (b) Hall mobility of Ga-doped ZnO layers as a function of the carrier concentration. The ZnO films were grown epitaxially on lattice-matched ScAlMg04 (SCAM) by Makino et al. [64], In (a) the calculated mobilities for acoustical, polar-optical, piezoelectric, and ionized impurity scattering are shown, together with the total theoretical mobility. In (b) the solid curve is the fit curve (2.24) from Fig. 2.6, while the dashed line is the theoretical curve, calculated by Makino et al. [64]. The dotted line was calculated for transport across depletion regions at grain barriers (see Sect. 2.2.3), also present in epitaxial films [106]... 

As mentioned in the preceding section the mobility of degenerately-doped zinc oxide (as well as of other TCO materials and semiconductors) is limited by ionized impurity scattering in homogeneously-doped materials. Since about 30 years it is well known that the mobility can be increased by the so-called modulation doping method, introduced by Dingle et al. [179] for GaAs/C.ai, Af As superlattice structures (for a review see [180]). 

Fig. t(..1-95 GaAs. Temperature variation of Hall mobility at 5 kG for three n-GaAs samples. In the temperature range from 300 K to 77 K, the electron mobility of sample a is dominated by polar optical scattering. Samples b and c show increased effects of ionized-impurity scattering [1.88]... 

ZnO-based heterostructures, which contain magnetic impurities in the barrier layer, were grown on c-cut sapphire substrates by pulsed laser deposition by Edahiro et al. [165]. The temperature dependence of the mobility of the Zrio.gMno jO/ZnO heterostructure exhibits the suppression of ionized impurity scattering below 100 K as shown in Figure 1.36. The carrier concentration and the mobility measured at... 

This process describes the scattering of free carriers by the screened Coulomb potential of charged impurities (dopants) or defects theoretically treated already in 1946 by Conwell [74,75], later by Shockley [10] and Brooks and Herring [76,77]. In 1969, Fistul gave an overview on heavily-doped semiconductors [78]. A comprehensive review of the different theories and a comparison to the experimental data of elemental and compound semiconductors was performed by Chattopadhyay and Queisser in 1980 [79]. For nondegenerate semiconductors the ionized impurity mobility is given by [79] ... 

At carrier densities above 1020 cm-3 the ionized impurities form clusters with a higher scattering power, which is proportional to the square of the cluster charge Z, further reducing the mobility, thus the parameter clustering mobility was introduced by Klassen [103,104]. It is interesting to note that though the lattice mobilities of silicon and ZnO are very different, the... 

Accordingly, the mobility decreases with temperature. The mobility influenced by scattering of electrons (or holes) at ionized impurities can be described [2, 7] by... 

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