Large-Area Hybrid Substrates for HgCdTe Infrared Detectors

The HgTe-CdTe system represents an excellent platform for infrared detection applications: its direct band gap E0 spans a 1.9 eV range from -0.3 eV (HgTe) to 1.6 eV (CdTe) and the nearly identical lattice constant between the two binary compounds makes it easy to grow intermediate random Hg1-xCdxTe alloys with continuously tunable optical properties between HgTe and CdTe. Unfortunately, however, HgTe-CdTe (MCT) suffers from very severe shortcomings, including use of high cost substrates and its difficult integration with Si-technology. Here we present a new approach to overcome some of these limitations and achieve direct integration of lattice mismatched HgTe-CdTe semiconductors with Si technologies. Our proposed program focuses on fabrication of lattice engineered virtual substrates and buffer layers based on the newly developed (Si)-Ge1-xSnx alloy system. These materials are grown on silicon substrates with exceptional crystallographic and morphological quality and possess random diamond cubic structures. This work has significant potential because the proposed templates can be fully integrated with silicon and their composition can be varied to cover a wide range of tunable lattice parameters (above that of Ge) and thermal expansions coefficients that approach those of HgCdTe.