Effects of mosaic structure on the physical properties of CdZnTe crystals

Mosaic structure in CdZnTe crystals was identified by using scanning electron microscopy (SEM), then the effects of mosaic structure on the physical properties were studied by means of high resolution X-ray diffraction (HRXRD), I-V characterization, and Fourier transform infrared (FT-IR) measurements. X-ray studies suggest that mosaic structure has a slightly different orientation from the main part of the sample. In FTIR measurements, IR transmittance of CdZnTe wafer with mosaic structure in the wavenumber between 500 and 1100 cm^-1 is only about 4%. From 1100 to 4000 cm^-1, it increases gradually to about 50%. Analysis of the low IR transmittance is discussed using the theory of free carrier absorption. I-V curve of CdZnTe wafer with mosaic structure exhibited piezoresistance characteristic. This characteristic can be considered as a transition to the space charge limited regime due to carriers injecting at the mosaic structure. By analogy with Schottky barrier behavior, we calculated interface barriers of CdZnTe wafer containing mosaic structure and the mosaic structure free wafer, which are 0.78 and 0.98 eV, respectively.