NONDESTRUCTIVE CHARACTERIZATION OF HG1-XCDXTE LAYERS WITH N-P STRUCTURES BY MAGNETO-THERMOELECTRIC MEASUREMENTS

The thermoelectric properties of n-type Hg0.79Cd0.21Te(MCT) and of MCT layers with n-p structure have been investigated in transverse (B per pendicular to del T) and longitudinal (B parallel to del T) magnetic f ields (0 less than or equal to B less than or equal to 16 kG) using th e lateral gradient method at temperatures between 10 and 300K. The exp erimental results were analyzed by considering the contributions of el ectrons and holes to the magneto-thermoelectric effect and the scatter ing mechanisms involved. The analysis is based on a nonparabolic condu ction 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 < 30K) and weak magnetic fields (B < 2kG) at low temperatures (T < 20K). Longitudinal (LO) phon ons were shown to prevail in the electron scattering at high temperatu res (T > 50K) 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 magnetop honon oscillations due to LO-phonon scattering from both HgTe and CdTe phonons. The transverse magnetoresistance (TMR) of then-type layers i n the quantum region has been found to be linearly dependent on the ma gnetic 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 par ticularly useful in determining the doping and composition of the cons tituent layers of MCT n-p structures.