Low-Cost Lattice Matching Si Based Composite Substrates for HgCdTe
ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
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A new class of low-cost composite substrate based on ternary alloy CdSexTe1 x211Si211 has been developed using molecular beam epitaxy MBE. Composition of the alloy can be tuned to exactly match the lattice of HgCdTe epilayer to minimize the generation of dislocations at the interface. The growth of CdSeTe was performed using a compound CdTe effusion source and an elemental Se effusion source. The alloy composition x of the CdSexTe1 x ternary compound was controlled through the SeCdTe flux ratios. Our results indicated that the crystalline quality of CdSeTe decreases as the alloy composition increases, possibly due to an alloy disordering effect. A similar trend was observed for the CdZnTe ternary alloy system. However, the alloy disordering effect in CdSeTe was found to be less severe than that in CdZnTe. We have carried out the growth of CdSeTe on Si at different temperatures. An optimized growth window was established for CdSeTe on Si211 to achieve high crystalline quality CdSeTeSi layers with 4 Se. The as-grown layers exhibited excellent surface morphology, low surface defect density less than 500 cm 2, and low x-ray full width at half maximum FWHM values near 100 arcsec. Additionally, CdSeTeSi layer exhibited excellent lateral uniformity.