Fabrication and characterization of two-color midwavelength/long wavelength HgCdTe infrared detectors

Abstract

High-performance 20-mm unit-cell two-color detectors using an n-p 1 -n HgCdTe triple-layer heterojunction (TLHJ) device architecture grown by molecular beam epitaxy (MBE) on (211)-oriented CdZnTe substrates with midwavelength (MW) infrared and long wavelength (LW) infrared spectral bands have been demonstrated. Detectors with nominal MW and LW cut-off wavelengths of 5.5 mm and 10.5 mm, respectively, exhibit 78 K LW performance with .70 % quantum efficiency, reverse bias dark currents below 300 pA, and RA products (zero field of view, 150-mV bias) in excess of 1 3 10 3 Vcm 2 . Temperaturedependent current-voltage (I-V) detector measurements show diffusion-limited LW dark current performance extending to temperatures below 70 K with good operating bias stability (150 mV 6 50 mV). These results reflect the successful implementation of MBE-grown TLHJ detector designs and the introduction of advanced photolithography techniques with inductively coupled plasma (ICP) etching to achieve high aspect ratio mesa delineation of individual detector elements with benefits to detector performance. These detector improvements complement the development of high operability large format 640 3 480 and 1280 3 720 two-color HgCdTe infrared focal plane arrays (FPAs) to support third generation forward looking infrared (FLIR) systems.

New material systems for third generation infrared photodetectors

“…A variation on the original back to back concept was implemented using HgCdTe at Rockwell [112] and Santa Barbara Research Center [113]. Following the successful demonstration of multispectral detectors in LPE-grown HgCdTe devices [113], the MBE and MOCVD techniques have been used for the grown of a variety of multispectral detectors at Raytheon [27,[114][115][116][117], BAE Systems [118], Leti [28,30,[119][120][121], Selex and QinetiQ [29,122,123], DRS, [26,124,125] Teledyne and NVESD [126,127]. For more than a decade a steady progression have been made in a wide variety of pixel size (to as small as 20 µm.…”

Plasma Passivation Etching for HgCdTe

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] However, ICP plasma processing, used in HgCdTe, is still maturing and continued research is needed. 4,7,14 ICP plasma processing may also be used to replace conventional wet chemical clean-up, and even be used in the surface preparation for epitaxy of II-VI materials. Producing plasma processes that can be used to delineate pixels, clean surfaces, and even produce epi-ready surfaces, would allow HgCdTe to become more manufacturable.…”

Two-colour HgCdTe infrared detectors operating above 200 K

“…In recent years, the realization of dual-band HgCdTe infrared detectors has been the core of intensive research and technological developments [3][4][5][6][7][8][9]. The detection in two different infrared bands or at two different wavelengths within the same band, allows the absolute temperature determination of an infrared scene, assuming a constant emissivity over the spectral range.…”

“…Previously, the multilayer approach has been usually fabricated using molecular beam epitaxy (MBE) [4][5][6]9]. However, an alternative growth technique, metaloorganic chemical vapour deposition (MOCVD), also allows the growth of multilayer structures with excellent control of composition and doping profiles [8].…”