<font>GaAs/AlGaAs</font> MULTI-QUANTUM WELL-BASED INFRARED FOCAL PLANE ARRAYS  FOR INFRARED IMAGING APPLICATIONS

Gunapala, Sarath D.; Bandara, S. V.

doi:10.1142/s0129156402001678

Cited by 6 publications

(6 citation statements)

References 17 publications

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“…In addition, it is difficult to fabricate random reflectors for shorter wavelength detectors relative to very long-wavelength detectors (i.e., 15 µm) due to the fact that feature sizes of random reflectors are linearly proportional to the peak wavelength of the detectors. For example, the minimum feature sizes of the random reflectors of 15 µm cutoff and 5 µm cutoff FPAs were 1.25 and 0.3 µm respectively, and it is difficult to fabricate sub-micron features by contact photolithography [16].…”

Section: × 1024 Pixel Mwir Qwip Focal Plane Arraymentioning

confidence: 99%

1024 × 1024 pixel mid-wavelength and long-wavelength infrared QWIP focal plane arrays for imaging applications

Gunapala

Bandara

Liu

et al. 2005

Semicond. Sci. Technol.

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Mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) 1024 × 1024 pixel quantum well infrared photodetector (QWIP) focal planes have been demonstrated with excellent imaging performance. The MWIR QWIP detector array has demonstrated a noise equivalent differential temperature (NE T) of 17 mK at a 95 K operating temperature with f/2.5 optics at 300 K background and the LWIR detector array has demonstrated a NE T of 13 mK at a 70 K operating temperature with the same optical and background conditions as the MWIR detector array after the subtraction of system noise. Both MWIR and LWIR focal planes have shown background limited performance (BLIP) at 90 K and 70 K operating temperatures respectively, with similar optical and background conditions. In this paper, we will discuss the performance in terms of quantum efficiency, NE T , uniformity, operability and modulation transfer functions.

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Section: × 1024 Pixel Mwir Qwip Focal Plane Arraymentioning

confidence: 99%

1024 × 1024 pixel mid-wavelength and long-wavelength infrared QWIP focal plane arrays for imaging applications

Gunapala

Bandara

Liu

et al. 2005

Semicond. Sci. Technol.

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“…Charge injection efficiency becomes worst at very low background flux, but limited by dark current for QWIP detector, i.e., the dark current keeps the pixel on. This initial array gave excellent images with 99.98% of the pixels working (number of dead pixels % 1000), again demonstrating the high yield of GaAs technology [11][12][13][14][15][16][17].…”

Section: Lwir Qwip Focal Plane Arraymentioning

confidence: 99%

“…The digital acquisition resolution of the camera is 14-bits, which determines the instantaneous dynamic range of the camera (i.e., 16,384). However, the dynamic range of QWIP is 85 Decibels.…”

Section: Mwir Qwip Focal Plane Arraymentioning

confidence: 99%

“…10 shows a picture of the prototype portable megapixel QWIP camera. The digital data acquisition resolution of the camera is 14-bits, which determines the instantaneous dynamic range of the camera (i.e., 16,384). The preliminary data taken from a test setup has shown mean system NETD of 16 mK at an operating temperature of T = 72 K and bias V B = À1 V, for a 300 K background.…”

Section: Lwir Qwip Focal Plane Arraymentioning

confidence: 99%

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Development of mid-wavelength and long-wavelength megapixel portable QWIP imaging cameras

Gunapala

Bandara

Liu

et al. 2005

Infrared Physics & Technology

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“…In fact Bethea et al [2] have demonstrated charge injection efficiencies approaching 90%. Charge injection efficiency can be obtained from [3,[9][10].…”

Section: X1024 Pixel Mwir Qwip Focal Plane Arraymentioning

confidence: 99%

Mid-wavelength infrared 1024x1024 pixel QWIP focal plane array

et al. 2004

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A mid-wavelength 1024x1024 pixel quantum well infrared photodetector (QWIP) focal plane array has been demonstrated with excellent imagery. Noise equivalent differential temperature (NETD) of 19 mK was achieved at 95K operating temperature with f/2.5 optics at 300K background. This focal plane array has shown background limited performance (BLIP) at 90K operating temperature with the same optics and background conditions. In this paper, we will discuss its performance in quantum efficiency, NETD, uniformity, and operability.A quantum well designed to detect infrared (IR) light is called a quantum well infrared photodetector (QWIP). An elegant candidate for QWIP is the square quantum well of basic quantum mechanics [1]. Each period of the multi-quantum well (MQW) structure consists of coupled quantum wells of 40 Å containing 10 Å GaAs, 20 Å In 0.3 Ga 0.7 As, and 10 Å GaAs layers (doped n = 5x10 17 cm -3 ) and a 40 Å barrier of Al 0.3 Ga 0.7 As between coupled quantum wells, and a 400 Å barrier of Al 0.3 Ga 0.7 As. Stacking many identical periods (typically 50) together increases photon absorption. Ground state electrons are provided in the detector by doping the GaAs well layers with Si (see Fig. 1). This photosensitive MQW structure is sandwiched between 0.5 µm GaAs top and bottom contact layers doped n = 5x10 17 cm -3 , grown on a semiinsulating GaAs substrate by molecular beam epitaxy (MBE). Then a 0.7 µm thick GaAs cap layer on top of a 300 Å Al 0.3 Ga 0.7 As stop-etch layer was grown in situ on top of the device structure to fabricate the light coupling optical cavity [2][3][4][5].The MBE grown material was tested for absorption efficiency using a Fourier Transform Infrared (FTIR) spectrometer. The experimentally measured absorption quantum efficiency of this material at room temperature was 19%. The epitaxially grown material was processed into 200 µm diameter mesa test structures (area = 3.14x10 -4 cm 2 ) using wet chemical etching, and Au/Ge ohmic contacts were evaporated onto the top and bottom contact layers.The detectors were back illuminated through a 45° polished facet [5-7] and a responsivity spectrum is shown in Fig. 2. The responsivity of the detector peaks at 4.6 µm and the peak responsivity (Rp) of the detector is 170 mA/W at bias V B = -2 V. The spectral width and the cutoff wavelength are ∆λ/λ = 15% and λ c = 5.1 µm respectively. The peak quantum efficiency was 19% at bias V B = -2 V for a 45° double pass. The lower quantum efficiency is due to the lower Fig 1. Schematic diagram of the conduction band in a bound-toquasibound QWIP. A couple quantum well structure has been used to broaden the responsivity spectrum.

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GaAs/AlGaAs MULTI-QUANTUM WELL-BASED INFRARED FOCAL PLANE ARRAYS FOR INFRARED IMAGING APPLICATIONS

Cited by 6 publications

References 17 publications

1024 × 1024 pixel mid-wavelength and long-wavelength infrared QWIP focal plane arrays for imaging applications

1024 × 1024 pixel mid-wavelength and long-wavelength infrared QWIP focal plane arrays for imaging applications

Development of mid-wavelength and long-wavelength megapixel portable QWIP imaging cameras

Mid-wavelength infrared 1024x1024 pixel QWIP focal plane array

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