Role of thermal expansion matching in CdTe heteroepitaxy on highly lattice-mismatched substrates

We report on the significance of thermal expansion mismatch in the heteroepitaxial growth of CdTe on highly lattice-mismatched substrates. Such substrates including Si, Ge, or GaAs are desirable for CdTe buffer layer growth and subsequent deposition of HgCdTe infrared absorber layers. Besides lattice misfit, the thermal mismatch associated with these systems can produce additional strain and defects at low or elevated temperatures. However, little work has been done towards documenting and understanding these effects. Experimental evidence of thermal-expansion-dependent residual stress is presented for CdTe/Si(2 1 1), CdTe/Ge(2 1 1), and CdTe/GaAs(2 1 1) films based on X-ray diffraction studies. The experimental results are also compared with residual stress calculations based on known material properties. These results may play a vital role in the design and development of HgCdTe detectors for large-format, infrared focal plane arrays (FPA).