Multispectral IR detection modules and applications

Abstract

This paper is intended to present firstly the current status at AIM on quantum well (QWIP) and antimonide superlattices (SL) detection modules for multi spectral ground and airborne applications in the high performance range i.e. for missile approach warning systems and secondly presents possibilities with long linear arrays i.e. 576x7 MCT to measure spectral selective in the 2 -11µm wavelength range.QWIP and antimonide based superlattice (SL) modules are developed and produced in a work share between AIM and the Fraunhofer Institute for Applied Solid State Physics (IAF). The sensitive layers are manufactured by the IAF, hybridized and integrated to IDCA or camera level by AIM. In case of MCT based modules, all steps are done by AIM.QWIP dual band or dual color detectors provide good resolution as long as integration times in the order of 5-10ms can be tolerated. This is acceptable for all applications where no fast motions of the platform or the targets are to be expected.For spectral selective detection, a QWIP detector combining 3-5 µm (MWIR) and 8-10 µm (LWIR) detection in each pixel with coincident integration has been developed in a 384x288x2 format with 40 µm pitch. Excellent thermal resolution with NETD < 30 mK @ F/2, 6.8 ms for both peak wavelengths (4.8 µm and 8.0 µm) has been achieved. Thanks to the well established QWIP technology, the pixel outage rates even in these complex structures are well below 0.5% in both bands. The spectral cross talk between the two wavelength bands is equal or less than 1%. The substrate on the sensitive layer of the FPA was completely removed in this case and as a consequence the optical crosstalk in the array usually observed in QWIP arrays resulting in low MTF values was suppressed resulting in sharp image impression.For rapidly changing scenes -like e.g. in case of missile warning applications for airborne platforms -a material system with higher quantum efficiency is required to limit integration times to typically 1ms. AIM and IAF selected antimonide based type II superlattices (SL) for such kind of applications. The type II SL technology provides -similar to QWIPs -an accurate engineering of sensitive layers by MBE with very good homogeneity and potentially good yield and resistivity against high temperature application i.e. under processing or storage. While promising results on single SL pixels have been reported since many years, so far no SL based detection module could be realized with reasonable performances. IAF and AIM last year managed to realize first most promising SL based detectors. Fully integrated IDCAs with a MWIR SL single color device with 256x256 pixels in 40 µm pitch have been integrated and tested. In the next step the pitch was reduced to 24µm in a 384x288 pixel configuration. With this design and further improved technology a very good pixel operabilities with very low cluster sizes (≤ 4 pixel) and performances with quantum efficiencies as high as known from MCT is reached in the meantime.A dual color device based on SL technology on the exist...

Infrared Detectors for the Future

“…Also first dual band LWIR/VLWIR photodiodes [56] and dual band MWIR FPAs [57] have been demonstrated. These very promising results confirm that the antimonide SL technology is now competing with MBE HgCdTe dual colour technology.…”

New material systems for third generation infrared photodetectors

“…Both HgCdTe photodiodes [25][26][27][28][29][30] and QWIPs [31][32][33][34][35][36][37] offer the multicolour capability in the SWIR, MWIR and LWIR range. The performance figures of merit of state-of-the-art QWIP and HgCdTe FPAs are similar because the main limitations come from the readout circuits.…”

“…The first bispectral 288´384 MWIR InAs/GaSb camera has been demonstrated [35]. Figure 23 illustrates the device processing.…”

“…First 256´256 SL MWIR [35,71] Recently, the demonstration of a high performance type-II FPA with cutoff wavelength of 10 µm has been reported [72]. The surface leakage current of photodiodes is suppressed using a double heterostructure design.…”

“…), array formats (up to 1280´720) and spectral-band sensitivity (MWIR/MWIR, MWIR/LWIR and LWIR/LWIR). Recently, type II InAs/ GaInSb superlattices have emerged as third candidate for third generation infrared detectors [20,21,35,[39][40][41].…”