Assessment of n + np HgCdTe/CdZnTe-Based Midwave Infrared Radiation Structure for Small-Scale Focal Plane Array
摘要
For the development of a small-scale focal plane array based on n + np HgCdTe/CdZnTe (MCT/CZT), the extent of inhomogeneities and elemental distribution in the n + np region, as well as at the interface, were studied at the nanoscale and correlated with findings from microscale characterization, including electrical characterization. In the n + np region, boron ions depth measured by secondary ion mass spectroscopy aligned with transmission electron microscopy, i.e., 0.5 ± 0.1 µm. Line defects in highly damaged regions induced by boron ion bombardment extended up to 700 nm from the top surface to a depth, accompanied by a slight shift in the peak observed in the rocking curve. Higher tellurium concentration within 100 nm of the surface observed in transmission electron microscopy and confirmed by x-ray photoelectron spectroscopy and scanning electron microscopy. The effect of post-implant annealing on diffusion along depth and lateral have been studied using the differential Hall effect and laser beam-induced current measurement method, respectively. In implanted samples, resistivity significantly changed at 0.5 µm after highly damaged region removal, which was contingent upon various annealing conditions. The junction depth varied largely with drive-in parameters but remained stable at particular annealing parameters, while lateral diffusion length was minimized to 90 µm by annealing at 120 °C for 90 min. In sharply interfaced MCT/CZT, the effect of defects present at the interface on the electrical properties was localized within 2–3 µm, and the density of etch pits measured 5 × 105 cm−2 at the interface. Good spectral response was measured by Fourier-transform infrared spectroscopy on the planar test diode structure.