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1995
Journal Article
Titel
Nondestructive characterization of Hg1-xCdxTe layers with n-p structures by magneto-thermoelectric measurements.
Alternative
Zerstörungsfreie Charakterisierung von Hg1-xCdxTe-Schichten mit n-p-Strukturen durch magnetothermoelektrische Messungen
Abstract
The thermoelectric properties of n-type Hg0.79Cd0.21Te (MCT) and of MCT layers with n-p structure have been investigated in transverse (B perpendicular to Del T) and longitudinal (B// Del T) magnetic fields (0<or=B<or=16 kG) using the lateral gradient method at temperatures between 10 and 300 K. The experimental results were analyzed by considering the contributions of electrons and holes to the magneto-thermoelectric effect and the scattering mechanisms involved. The analysis is based on a nonparabolic conduction band and Landau quantization as well as empirical relations for the band gap, the intrinsic carrier density, and the magnetoresistance. For n-type MCT at low temperatures (10<T<30 K) and weak magnetic fields (B<2 kG), the transverse magneto-thermoelectric effect (TME) was seen to be dominated by electron scattering on ionized defects. Longitudinal acoustic phonon drag was found to affect the TME in strong magnetic fields (B>3 kG) at low temperatures (T<20 K). Longitudinal (LO ) phonons were shown to prevail in the electron scattering at higher temperatures (T>50 K) in weak magnetic fields. With increasing magnetic fields, the effect of LO-phonon scattering decreases, and eventually the TME becomes independent of electron scattering. The longitudinal magneto-thermoelectric effect of n-type MCT was also found to exhibit magnetophonon oscillations due to LO-phonon scattering from both HgTe and CdTe phonons. The transverse magnetoresistance (TMR) of the n-type layers in the quantum region has been found to be linearly dependent on the magnetic field. Owing to the TMR of the n-type layers, the variation of the TME of p-n multiple layers with magnetic field is much larger than the variation of the Seebeck coefficient with temperature. Thus, the sensitivity to p-type layers is considerably enhanced compared to that of the Seebeck coefficient. As a result, the TME has proved to be particularly useful in determining the doping and composition of the constituent lay e rs of MCT n-p structures.