In this work, the characteristics of metamorphic grown InGaAs based and InAs/GaSb/AlSb/GaSb Type-II superlattice based extended short wave infrared(eSWIR) detectors are reported. The InGaAs detector was a p-i-n photodiode(PD) with a planar structure, and the T2SL detector was an nBn barrier infrared diode with mesa structure. In case of InGaAs detector, the cutoff wavelength is 2.35 μm and average quantum efficiency(QE) in the 1.1-2.2μm spectral range is 70.1% under front-side illumination condition and 200 K operation. At 200K, the dark current density is 6.80×10-9 A/cm2 under -0.1 V bias and the expected peak specific detectivity is 2.33×1013 cm∙㎐ 1/2/W. In case of T2SL, the cutoff wavelength is 2.45 μm and average QE in the 1.1-2.2 μm spectral range is 51.3 % at 200 K. The dark current density at 200 K is 1.1×10-7 A/cm2 and the expected peak specific detectivity is 4.68×1012cm∙㎐ 1/2/W at 200 K. The 1280×1024 infrared focal plane array (FPA) with the pixel size of 10 μm is fabricated and hybridized with readout integrated circuit. The InGaAs FPA show relatively low operability due to defect or cross hatch pattern of wafer while its specific detectivity is higher than T2SL.
InGaAs detector for SWIR imaging is widely used for remote sensing, medical application, personal identification etc. To reduce the required power for various environmental condition, reducing dark current is crucial. The dark current of InGaAs detector is known to come from defects induced during the growth of wafers and the process to fabricate FPAs. Especially, when high temperature is applied for the diffusion of Zn to form p-type junction on n-type InP/InGaAs substrate, the diffusion barrier of Zn on the substrate experiences large expansion and add stress in the substrate. The induced stress will increase defects and increase dark current. In this work, to reduce the stress of the Zn diffusion barrier, balanced diffusion barrier with multiple layer is applied. By reducing the stress, the dark current density has reduced to below 10 nA/cm2, which is suitable for low power operation.
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