Relaxation-free HgCdTe heteroepitaxy via lattice-matching: X-ray reciprocal space mapping characterization and dual-color focal plane array performance validation

Abstract

As the preferred material for high-performance infrared detection, the device performance of mercury cadmium telluride (HgCdTe) fundamentally depends on the quality of heteroepitaxial films. The longitudinal segregation of Zn composition during CdZnTe ingot growth leads to inhomogeneous lattice constant distribution in sliced substrates. Lattice mismatch between the substrate and HgCdTe epilayer induces strain relaxation and dislocation multiplication, degrading the crystal quality of the epilayer. This study proposes a quantitative lattice-matching technique that achieves controlled lattice mismatch between CdZnTe substrates and target HgCdTe epilayers by designing gradient-varied lattice constant HgCdTe layers. Combined with high-resolution x-ray reciprocal space mapping technique, the lattice relaxation behavior in multilayer heterostructures has been systematically revealed. Experimental results demonstrate that films grown with the lattice-matching technique exhibit no lattice tilt (α=0), near-zero in-plane lattice mismatch (m||≈0%), and dislocation density within one order of magnitude (9.66×104 cm−2) compared to the CdZnTe substrate (6.44×104 cm−2), effectively suppressing dislocation multiplication during epitaxy. In contrast, directly grown HgCdTe films with target composition show lattice tilt (α=1.1075°), residual mismatch (m||=0.001 06%), and a two-order-of-magnitude increase in dislocation density relative to the substrate. The fabricated mid-/long-wavelength dual-color detectors demonstrated superior performance: operable pixel rates reaching 99.8% (mid-wavelength: 3.6−5.0 μm) and 99.7% (long-wavelength: 7.4−9.7 μm), with noise equivalent temperature difference (NETD) as low as 14.1 and 22.5 mK, respectively. This research provides key insights for achieving high-crystalline-quality HgCdTe epitaxy.