Carrier concentration, temperature

Ideal Performance and Cooling Requirements. Eree carriers can be excited by the thermal motion of the crystal lattice (phonons) as well as by photon absorption. These thermally excited carriers determine the magnitude of the dark current,/ and constitute a source of noise that defines the limit of the minimum radiation flux that can be detected. The dark carrier concentration is temperature dependent and decreases exponentially with reciprocal temperature at a rate that is determined by the magnitude of or E for intrinsic or extrinsic material, respectively. Therefore, usually it is necessary to operate infrared photon detectors at reduced temperatures to achieve high sensitivity. The smaller the value of E or E, the lower the temperature must be. 

Fig. 15. Excess carrier concentration in HgCdTe in a saturated Hg vapor as a function of temperature where the dashed line represents Hg vacancies. The extrinsic impurity concentration can be adjusted in the growth process from low 10 up to mid-10. Low temperature annealing reduces Hg vacancy...

As the temperature increases, the intrinsic carrier concentration rises exponentially so that at some point n ... 

More precise coefficients are available (33). At room temperature, cii 1.12 eV and cii 1.4 x 10 ° /cm. Both hole and electron mobilities decrease as the number of carriers increase, but near room temperature and for concentrations less than about 10 there is Htde change, and the values are ca 1400cm /(V-s) for electrons and ca 475cm /(V-s) for holes. These numbers give a calculated electrical resistivity, the reciprocal of conductivity, for pure sihcon of ca 230, 000 Hem. As can be seen from equation 6, the carrier concentration increases exponentially with temperature, and at 700°C the resistivity has dropped to ca 0.1 Hem. 

As mentioned above, the interpretation of CL cannot be unified under a simple law, and one of the fundamental difficulties involved in luminescence analysis is the lack of information on the competing nonradiative processes present in the material. In addition, the influence of defects, the surface, and various external perturbations (such as temperature, electric field, and stress) have to be taken into account in quantitative CL analysis. All these make the quantification of CL intensities difficult. Correlations between dopant concentrations and such band-shape parameters as the peak energy and the half-width of the CL emission currently are more reliable as means for the quantitative analysis of the carrier concentration. 

Evaporation temperature, c Ag atoms flow intensity, isotope method, atoms s l Current carrier concentration variation rate in the film, semiconductor sensor method, Vg- 10 , electrons s Ve... 

Precursor Impurities detected by plasma emission (ppm) Material grown and temperature (°C) Carrier concentration, 77K (cm-3)a Mobility, /i77[c (cm2 V-1 s f... 

The net carrier concentration, shown in Fig. 7.8, was obtained at a frequency of 100 kHz. DLTS spectra were recorded using reverse- and forward-bias modes in the temperature range of 80-350 K. In the re verse-bias mode, the devices were reverse biased from -1.2V to -0.2V, with a pulse width of 1 ms. Two hole (majority-carrier) trap levels were found in all the devices. These levels were designated as Hi at I iv+0.26 and H2, for which an activation energy could not be resolved. Upon minority-carrier injection (forward-bias mode), DLTS showed two additional electron (minority-carrier) traps, which are labeled Ei (Ec-0.1eV) and E2 (Ec-0.83eV) in Table 7.1. The spectra were measured at an emission time of 465.2 s and the width of the... 

Fig. 17 Temperature dependence of the hole mobility measured in an FET with (a) pentacene and (b) P3HT as active layers. Parameter Is the gate voltage. Data fitting using the Fishchuk et al. theory in [102] yields values for the mobility and the disorder potential extrapolated to zero electric field and zero carrier concentration. To is the Meyer-Nedel temperature (see text). From [102] with permission. Copyright (2010) by the American Institute of Physics...

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