This letter reports a 320×256 middle-wavelength infrared focal plane array operating at temperatures up to 200K based on an InAs quantum dot/InGaAs quantum well/InAlAs barrier detector grown on InP substrate by low pressure metal organic chemical vapor deposition. The device’s low dark current density and the persistence of the photocurrent up to room temperature enabled the high temperature imaging. The focal plane array had a peak detection wavelength of 4μm, a responsivity of 34mA∕W, a conversion efficiency of 1.1%, and a noise equivalent temperature difference of 344mK at an operating temperature of 120K.
We report a room temperature operating and high-performance InAs quantum-dot infrared photodetector on InP substrate and thermal imaging of 320× 256 focal plane array based on this device up to 200 K.OCIS code: (040.3060) Infrared; (040.5160) Photodetectors; (110.3080) Infrared imaging Self-assembled semiconductor quantum dots (QDs) [1], have attracted much attention because of their interesting properties and possible applications, such as quantum dot infrared photodetectors (QDIPs) [2][3][4]. QDIPs can be building blocks of focal plane arrays (FPAs) in infrared imaging systems which have been widely investigated for mid-infrared (3~5 µm) and long-infrared (8~12 µm) applications [5][6][7]. QDIPs have several potential advantages over conventional technologies and these advantages promise infrared detectors with high-temperature operation and high performance. However, most of the QDIPs reported so far in the literature have not met the expected high performance and have been working at temperatures in the range 77 K~200 K [5-7]. Here, we present a high-performance, room temperature operating mid-infrared photodetector based on InAs QDs embedded in Ga 0.47 In 0.53 As quantum wells (QWs) grown on top of Al 0.48 In 0.52 As barriers on an InP substrate [8]. We also report an FPA made from this kind of a QDIP.The device structure, as shown at the left in Fig. 1, was grown by low-pressure metalorganic chemical vapor deposition. The growth temperature of the entire device structure was 590 °C. The active region consisted of 25 stacks of InAs QD/GaInAs QW layers with 29 nm-AlInAs barrier layers. The InAs QDs on the AlInAs barrier layers were obtained by self-assembly based on the Stranski-Krastanow epitaxial growth mode. SI-InPsubstrate 0.5 µm-InPbuffer 1 µm-n-InPcontact (n=3×10 18 cm -3 ) 29 nm-AlInAs barrier 3.5 nm-GaInAsQW InAsQD 0.5 µm-n-InPcontact (n=3×10 18 cm -3 ) ×25 3.0 3.5 4.0 4.5 5.0 5.5 6.0 0 5 10 15 20 25 30 35 40 Photoresponse (a.u.) Wavelength µ µ µ µm 77 K (-5 V) 120 K (-5 V) 180 K (-5 V) 240 K (-5 V) RT (-2 V) 2.5 3.0 3.5 4.0 4.5 5.0 5.5 0 1 2 3 Room Temperature Photoreseponse (a.u.) Wavelength µ µ µ µm -2 V +1 V Fig. 1. (Left) Schematics of the QDIP device structure; (right) Relative photoresponse of the device at different temperatures measured by FTIR spectroscopy.We measured the spectral response at several temperatures and applied biases by using a Fourier transform infrared spectrometer in the normal incidence configuration without any optical coupling structures. In this device structure, both the InAs QD layers and GaInAs QW layers are involved in the infrared absorption process. In our device structure, we believe the initial state is not necessarily from a localized "pure" quantum dot state but from a delocalized "mixed" state of the quantum well and the quantum dot For all temperatures except room temperature, at an applied bias of -5 V (-2 V for room temperature), the peak around 4.1 µm was dominant in the spectral response, as shown in the right of Fig. 1. The strong sensitivity to the appl...
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