Imaging One-Dimensional and Two-Dimensional Planar Photodiode Detectors Fabricated by Ion Milling Molecular Beam Epitaxy CdHgTe

Authors: Haakenaasen, R.; Steen, H.; Selvig, E.; Lorentzen, T.; Van Rheenen, A.D.; Trosdahl-Iversen, L.; Syversen, H.; Hall, D.; Gordon, N.

Source: Journal of Electronic Materials, Volume 34, Number 6, June 2005 , pp. 922-927(6)

Publisher: Springer

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Abstract:

Imaging one-dimensional (1-D) and two-dimensional (2-D) arrays of midwavelength infrared (MWIR) and long-wavelength infrared (LWIR) planar photodiodes were fabricated by ion milling of vacancy-doped molecular beam epitaxy Cd_xHg_1−xTe layers. Sixty-four-element 1-D arrays of 26 × 26 μm² or 26 × 56 μm² diodes were processed. Zero-bias resistance-area values (R₀A) at 77 K of 4 × 10⁶ Ωcm² at cutoff wavelength λ_CO = 4.5 μm were measured, as well as high quantum efficiencies. To avoid creating a leakage current during ball bonding to the 1-D array diodes, a ZnS layer was deposited on top of the CdTe passivation layer, as well as extra electroplated Au on the bonding pads. The best measured noise equivalent temperature difference (NETD) on a LWIR array was 8 mK, with a median of 14 mK for the 42 operable diodes. The best measured NETD on a MWIR array was 18 mK. Two-D arrays showed reasonably good uniformity of R₀A and zero-bias current (I₀) values. The first 64 × 64 element 2-D array of 16 × 16 μm² MWIR diodes has been hybridized to read-out electronics and gave median NETD of 60 mK.

Keywords: CDHGTE; HGCDTE; CDZNTE; LONG-WAVELENGTH INFRARED (LWIR); MID-WAVELENGTH INFRARED (MWIR); ION MILLING; MOLECULAR BEAM EPITAXY; N-ON-P DIODES; PHOTODIODES; PLANAR DIODES; LINEAR ARRAY; TWO-DIMENSIONAL (2-D) ARRAY; IR DETECTOR