Quantum Dot Infrared Photodetectors Operating at Room Temperature: Modeling, Experiments and Analysis

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The important application for the infrared photodetectors is mainly thermal imaging by focal plane arrays (FPAs) for military and commercial purposes. So far, most mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) FPAs are based either on HgCdTe (MCT) or quantum well infrared photodetectors (QWIPs). Even though those technologies are well developed and have the state of the art performances, they have intrinsic weaknesses which are difficult to be overcome. Many researchers have searched new infrared photodetectors. One of the promising technologies is quantum dot infrared photodetectors (QDIP) based on self-assembled quantum dots. Self-assembled quantum dot is the very nanotechnology which is based on the novel physical phenomena and shows the possibility of promising new device concept. The objective of this work is to develop high performance and high operation temperature quantum dot infrared photodetectors based on high quality self assembled (Ga)InAs quantum dots on InP and GaAs substrates grown by low pressure metal organic chemical vapor deposition. At first, the unique physical properties of quantum dots will be discussed in terms of density of state, discrete energy levels and finally novel property "phonon bottleneck". And the method of fabrication of quantum dots and device structures and test procedures will be reviewed. At second, in order to understand the device design rules, the modeling of the important parameters will be developed. The parameters which will be discussed are energy levels, oscillator strengths of the transitions, responsivity, dark current, noise, gain and detectivity. The detailed analyses on one of InGaAs QD/InGaP/GaAs MWIR-QDIPs will be given to elucidate the physical understandings and give the direction for the improvement of the devices. At third, MWIR-QDIP structures based on the InAs/InP systems will be discussed. Especially the focus on the growth of the InAs quantum dots on various matrix layers on InP substrate will be made. At 77 K, the photoresponse showed the peak wavelength around 5 µm. The highest detectivity was 2.0×10^9 cmHz1/2 /W. Finally, the hybridization of the InAs quantum dot and the In0.53Ga0.47As quantum well was realized in InAs/InGaAs/InAlAs/InP system. The resulting device structure which is named as quantum dot-quantum well infrared photodetector (QDWIP) had high-performance and high operation temperature up to room temperature. The peak detection wavelength was observed at 4.1 µm. The peak responsivity and the specific detectivity at 120 K were 667 mA/W and 2.8×10^11 cmHz1/2/W respectively. Low dark current density and a high quantum efficiency of 35 % were obtained in this device. We will discuss how the quantum efficiency can be improved through quantum dot engineering

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  • 08/29/2018
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