Defect Reductions on Si Substrates for HgCdTe MBE Growth

Current state-of-the-art infrared focal plane arrays (IRFPAs) are based on HgCdTe material epitaxially grown on bulk CdZnTe substrates. The size of the IRFPAs is limited by the size of the available CdZnTe substrates and the thermal mismatch between CdZnTe and the Si readout circuit, which misaligns the photodiode array with respect to the circuit during heating and cooling cycles. Having HgCdTe fabricated on Si-based composite substrates would eliminate the aforementioned drawbacks related to the HgCdTe/CdZnTe system. Indeed, the use of Si-based substrates would also lower imager costs. While a large effort has been put forward to improve the quality of the HgCdTe grown on CdTe/Si, there still remains much room for further advancement. In the proposed effort, Episensors will develop new and innovative chemical mechanical polishing slurries and cleaning techniques that will yield higher quality Si(112) substrates. CdTe/Si layers will be grown in-house via molecular beam epitaxy and the growth of HgCdTe on CdTe/Si will take place at the University of Illinois at Chicago. We will employ advanced methods for characterizing the materials and devices to provide feedback for process optimization.