Quantum well infrared photodetectors (QWIPs) have gained maturity for large focal plane arrays (FPA) with excellent thermal resolution, low 1/f noise, low fixed-pattern noise, and high pixel operability. Due to their spectrally narrow absorption, QWIPs are particularly suitable for thermal imaging applications involving several atmospheric transmission bands or several colors within the same band. We report on our progress on dual-band QWIP FPAs with pixel-registered, simultaneous integration in both bands. The arrays with 384x288 pixels and 40 μm pitch are based on a photoconductive QWIP for the 3-5 μm regime (MWIR) and a photovoltaic "low-noise" QWIP for 8-12 μm (LWIR). Excellent noise-equivalent temperature differences of only 20.6 mK (LWIR) and 26.7 mK (MWIR) have been achieved at 6.8 ms integration time and f/2 aperture. In addition, we have investigated test devices with different gratings, and discuss their dual-band coupling efficiencies.

We report on the development and status of a dual-band QWIP FPA with 384×288 pixels and 40μm pitch for the 3–5μm (mid-wavelength infrared, MWIR) and 8–12μm (long-wavelength infrared, LWIR) spectral bands. The array is based on a photovoltaic “low-noise” QWIP for the LWIR and a photoconductive QWIP for the MWIR and allows for simultaneous integration of both bands on each pixel. Array histograms indicate a noise-equivalent temperature difference as low as 17mK for the MWIR band and 43mK for the LWIR band at an integration time of 7.6 ms. In addition, we have investigated test devices with different gratings, geometries, and sizes and discuss some tradeoffs for dual-band diffraction gratings.

A dual-band focal plane array (FPA) for the 8-12 rhom and 3 5 pm atmospheric windows with simultaneous integration in both spectral bands on each pixel is reported. The FPA is based on quantum well infrared photodetectors and comprises 384 x 288 pixels with 40 mum pitch. At 7.6 ms integration time and an f/2 aperture, the FPA achieves excellent thermal resolution with noise-equivalent temperature differences of 17 mK (3-5 mum) and 43 mK (8-12 mum).

For high performance IR imaging and seeker systems AIM has established a high yield and reproducible HgCdTe detector technology. For continuous improvement of detector performance, yield and reliability, key processes have been optimized and new approaches have been developed. By a superior CdZnTe Bridgman growth process, dislocation densities <1×105cm−2 in substrate and epitaxial layer are achieved for all substrates, ensuring high performance focal-plane-arrays, particularly for λCO=11.5μm arrays. A new guard ring approach for planar diodes, created by a n+-region in pixel spacing area reduces pixel crosstalk and improves modulation transfer function. For long linear arrays, a multichip-module-technique has been developed, which meets the demands for high temperature-cycle-reliability. In addition, a cycle-to-failure model has been established by cooldown tests on AIM-FPA's to predict cycle-to-failure at existing FPA approach or maximum allowable strain at demanded cycles-to-failure specification.

To meet the demands for high performance HgCdTe detectors at high yield and producibility, key processes have been optimized and new approaches have been developed. By a superior CdZnTe Bridgman growth process, dislocation densities <1x105cm-2 in substrate and epitaxial layer are achieved for all substrates, ensuring high performance Focal-Plane-Arrays, particularly for (lambda) CO=11,5 micrometers arrays. A new guard ring approach for planar diodes, created by a n+-region in pixel spacing area reduces pixel crosstalk and improves Modulation Transfer Function. For high thermal cycles of the FPA, the flip-chip- technique has been optimized, leading to >2000 cycles for 640x512-FPA's. Producibility and reliability of AIM's MCT FPA technology are demonstrated.