Molecular beam epitaxial growth and performance of integrated multispectral HgCdTe photodiodes for the detection of mid-wave infrared radiation

Abstract

In situ doped HgCdTe two-color detectors with the n—p—n geometry were grown by molecular beam epitaxy, for the simultaneous detection of two closely spaced bands in the mid-wave infrared spectrum. The average near-surface etch pit densities in these layers were 5 × 10 6 cm −2 which is a factor of 10 higher than that observed for the lattice-matched growth of Hg 1− x Cd x Te ( x = 0.22) layer on Cd 0.96Zn 0.04Te substrates. The 0.04% lattice mismatch between the Hg 1− x Cd x Te ( x = 0.35) epilayer and the Cd 0.96Zn 0.04Te substrate produces plastic deformation of the epilayer which results in an increased dislocation densities in the epilayer. The alloy composition across the device structure along the growth direction was determined by secondary ion mass spectrometric analysis, and deviated by less than 1% from the target. The device structures were processed as diodes with the mesa architecture and tested. The spectral response of the detectors at 77 K was characterized by sharp turn off at 3.7 and 4.4 μm. R o A values in excess of 1 × 10 6 Ω cm 2 and quantum efficiencies greater than 75% were measured for diodes in each band.