Publications by    
Page 1  (11 Items)

1.  
Gain and recombination dynamics of quantum-dot infrared photodetecto
Gain and recombination dynamics of quantum-dot infrared photodetecto
H. Lim, B. Movaghar, S. Tsao, M. Taguchi, W. Zhang, A.A. Quivy, and M. Razeghi
Virtual Journal of Nanoscale Science & Technology-- December 4, 2006reprint
 
2.  
Gain and recombination dynamics of quantum-dot infrared photodetectors
Gain and recombination dynamics of quantum-dot infrared photodetectors
H. Lim, B. Movaghar, S. Tsao, M. Taguchi, W. Zhang, A.A. Quivy, and M. Razeghi
Physical Review B, 74 (20)-- November 15, 2006
In this paper we present a theory of diffusion and recombination in QDIPs which is an attempt to explain the recently reported values of gain in these devices. We allow the kinetics to encompass both the diffusion and capture rate limited regimes of carrier relaxation using rigorous random walk and diffusion methods. The photoconductive gains are calculated and compared with the experimental values obtained from InGaAs/InGaP/GaAs and InAs/InP QDIPs using the generation-recombination noise analysis. reprint
 
3.  
High performance mid-wavelength quantum dot infrared photodetectors for focal plane arrays
High performance mid-wavelength quantum dot infrared photodetectors for focal plane arrays
M. Razeghi, H. Lim, S. Tsao, M. Taguchi, W. Zhang and A.A. Quivy
SPIE Conference, San Diego, CA, Vol. 6297, pp. 62970C-- August 13, 2006
Quantum dot infrared photodetectors (QDIPs) have recently emerged as promising candidates for detection in the middle wavelength infrared (MWIR) and long wavelength infrared (LWIR) ranges. Here, we report our recent results for mid-wavelength QDIPs grown by low-pressure metalorganic chemical vapor deposition. Three monolayer of In0.68Ga0.32As self-assembled via the Stranski-Krastanov growth mode and formed lens-shaped InGaAs quantum dots with a density around 3×1010 cm-2. The peak responsivity at 77 K was measured to be 3.4 A/W at a bias of -1.9 V with 4.7 µm peak detection wavelength. Focal plane arrays (FPAs) based on these devices have been developed. The preliminary result of FPA imaging is presented. reprint
 
4.  Quantum Dots in GaInP/GaInAs/GaAs for Infrared Sensing
M. Razeghi, H. Lim, S. Tsao, M. Taguchi, W. Zhang, and A.A. Quivy
Advances in Science and Technology 51-- June 4, 2006
Quantum dots grown by epitaxial self-assembly via Stranski- Krastanov growth mode have many favorable properties for infrared sensing. Because of their very small size and three-dimensional confinement, the electronic energy levels are quantized and discrete. These quantum effects lead to a unique property, “phonon bottleneck”, which might enable the high operating temperature of infrared sensing which usually requires cryogenic cooling. Here we report a focal plane array (FPA) based on an epitaxial self-assembled quantum dot infrared detector (QDIP). The device structure containing self-assembled In0.68Ga0.32As quantum dots with a density around 3×1010 cm-2 was grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). Using different structures, we successfully developed QDIPs with a peak photoresponse around 5 μm and 9 μm. High peak detectivities were achieved at 77 K from both QDIPs. By stacking both device structures, we demonstrated a two-color QDIP whose peak detection wavelength could be tuned from 5 μm to 9 μm by changing the bias. 256×256 detector arrays based on 5 μm and 9 μm-QDIPs were fabricated with standard photolithography, dry etching and hybridization to a read-out integrated circuit (ROIC). We demonstrated thermal imaging from our FPAs based on QDIPs.
 
5.  
Quantum-dot infrared photodetectors and focal plane arrays
Quantum-dot infrared photodetectors and focal plane arrays
M. Razeghi, H. Lim, S. Tsao, M. Taguchi, W. Zhang, and A.A. Quivy
SPIE Infrared Technology and Applications Conference, April 17-21, 2006, Orlando, FL Proceedings – Infrared Technology and Applications XXXII, Vol. 6206, p. 62060I-1-- April 21, 2006
We report our recent results about mid-wavelength infrared quantum-dot infrared photodetectors (QDIPs) grown by low-pressure metalorganic chemical vapor deposition. A very high responsivity and a very low dark current were obtained. A high peak detectivity of the order of 3×1012 Jones was achieved at 77 K. The temperature dependent device performance was also investigated. The improved temperature insensitivity compared to QWIPs was attributed to the properties of quantum dots. The device showed a background limited performance temperature of 220 K with a 45° field of view and 300K background. reprint
 
6.  
High-detectivity quantum-dot infrared photodetectors grown by metal-organic chemical-vapor deposition
High-detectivity quantum-dot infrared photodetectors grown by metal-organic chemical-vapor deposition
J. Szafraniec, S. Tsao, W. Zhang, H. Lim, M. Taguchi, A.A. Quivy, B. Movaghar and M. Razeghi
Applied Physics Letters 88 (121102)-- March 20, 2006
A mid-wavelength infrared photodetector based on InGaAs quantum dots buried in an InGaP matrix and deposited on a GaAs substrate was demonstrated. Its photoresponse at T=77 K was measured to be around 4.7 μm with a cutoff at 5.5 μm. Due to the high peak responsivity of 1.2 A/W and low dark-current noise of the device, a specific peak detectivity of 1.1 x 1012 cm·Hz½·W−1 was achieved at −0.9 V bias reprint
 
7.  InGaAs/InGaP Quantum-Dot Photodetector with a High Detectivity
H. Lim, S. Tsao, M. Taguchi, W. Zhang, A. Quivy and M. Razeghi
SPIE Conference, San Jose, CA, Vol. 6127, pp. 61270N-- January 23, 2006
Quantum-dot infrared photodetectors (QDIPs) have recently been considered as strong candidates for numerous applications such as night vision, space communication, gas analysis and medical diagnosis involving middle and long wavelength infrared (MWIR and LWIR respectively) operation. This is due to their unique properties arising from their 3-dimensional confinement potential that provides a discrete density of states. They are expected to outperform quantum-well infrared photodetectors (QWIPs) as a consequence of their natural sensitivity to normal incident radiation, their higher responsivity and their higher-temperature operation. So far, most of the QDIPs reported in the literature were based on the InAs/GaAs system and were grown by molecular beam epitaxy (MBE). Here, we report on the growth of a high detectivity InGaAs/InGaP QDIP grown on a GaAs substrate using low-pressure metalorganic chemical vapor deposition (MOCVD). reprint
 
8.  InAs quantum dot infrared photodetectors on InP by MOCVD
W. Zhang, H. Lim, M. Taguchi, A. Quivy and M. Razeghi
SPIE Conference, San Jose, CA, Vol. 6127, pp. 61270M -- January 23, 2006
We report our recent results of InAs quantum dots grown on InP substrate by low-pressure metalorganic chemical vapor deposition (MOCVD) for the application of quantum dot infrared photodetector (QDIP). We have previously demonstrated the first InP-based QDIP with a peak detection wavelength at 6.4 µm and a detectivity of 1010 cm·Hz½/W at 77K. Here we show our recent work toward shifting the detection wavelength to the 3-5 µm middlewavelength infrared (MWIR) range. The dependence of the quantum dot on the growth conditions is studied by atomic force microscopy, photoluminescence and Fourier transform infrared spectroscopy. Possible ways to increase the quantum efficiency of QDIPs are discussed. reprint
 
9.  Focal plane arrays based on quantum dot infrared photodetectors
Manijeh Razeghi; Wei Zhang; Ho-Chul Lim; Stanley Tsao; John Szafraniec; Maho Taguchi; Bijan Movaghar
Proc. SPIE 5838, Nanotechnology II, 125 (June 28, 2005);-- June 28, 2005
Here we report the first demonstrations of infrared focal plane array (FPA) based on GaAs and InP based quantum dot infrared photodetectors (QDIPs). QDIPs are extension of quantum well infrared photodetectors (QWIPs) and are predicted to outperform QWIPs due to their potential advantages including normally incident absorption, higher responsivity and high temperature operation. Two material systems have been studied: InGaAs/InGaP QDIPs on GaAs substrates and InAs QDIP on InP substrates. An InGaAs/InGaP QDIP has been grown on GaAs substrate by LP-MOCVD. Photoresponse was observed at temperatures up to 200 K with a peak wavelength of 4.7 μm and cutoff wavelength of 5.2 μm. A detectivity of 1.2x1011 cm·Hz1/2/W was obtained at T=77 K and bias of -0.9 V, which is the highest for QDIPs grown by MOCVD. An InAs QDIP structure has also been grown on InP substrate by LP-MOCVD. Photoresponse of normal incidence was observed at temperature up to 160K with a peak wavelength of 6.4 μm and cutoff wavelength of 6.6 μm. A detectivity of 1.0x1010 cm·Hz1/2/W was obtained at 77K at biases of -1.1 V, which is the first and highest detectivity reported for QDIP on InP substrate. 256×256 detector arrays were fabricated first time in the world for both the GaAs and InP based QDIPs. Dry etching and indium bump bonding were used to hybridize the arrays to a Litton readout integrated circuit. For the InGaAs/InGaP QDIP FPA, thermal imaging was achieved at temperatures up to 120 K. At T=77K, the noise equivalent temperature difference (NEDT) was measured as 0.509K with a 300K background and f/2.3 optics. For the InP based QDIPs, thermal imaging was achieved at 77 K. reprint
 
10.  High Detectivity InAs Quantum-Dot Infrared Photodetectors Grown on InP by Metalorganic Chemical Vapor Deposition
W. Zhang, H. Lim, M. Taguchi, S. Tsao, B. Movaghar, and M. Razeghi
Applied Physics Letters, 86 (19)-- May 9, 2005
We report a high-detectivity InAs quantum-dot infrared photodetector. The InAs quantum dots were grown by self-assembly on InP substrates via low-pressure metal–organic chemical–vapor deposition. Highly uniform quantum dots with a density of 4×1010 cm2 were grown on a GaAs/InP matrix. Photoresponse was observed at temperatures up to 160 K with a peak of 6.4 µm and cutoff of 6.6 µm. Very low dark currents and noise currents were obtained by inserting Al0.48In0.52As current blocking layers. The background-limited performance temperature was 100 K. A detectivity of 1.0×1010 cm·Hz½/W was obtained at 77 K with a bias of –1.1 V. reprint
 
11.  High performance InAs quantum dot infrared photodetectors (QDIP) on InP by MOCVD
W. Zhang, H. Lim, M. Taguchi, S. Tsao, J. Szafraniec, B. Movaghar, M. Razeghi, and M. Tidrow
SPIE Conference, Jose, CA, Vol. 5732, pp. 326-- January 22, 2005
Inter-subband detectors such as quantum well infrared photodetectors (QWIP) have been widely used in infrared detection. Quantum dot infrared photodetectors (QDIPs) have been predicted to have better performance than QWIPs including higher operation temperature and normal incidence detection. Here we report our recent results of InAs QDIP grown on InP substrate by low-pressure metalorganic chemical vapor deposition (MOCVD). The device structures consist of multiple stacks of InAs quantum dots with InP barriers. High detectivities in the range of 1010cm·Hz1/2/W were obtained at 77K. The measurements at higher temperatures show better temperature dependent performance than QWIP. However, the performances of QDIPs are still far from the expected. One of the reasons is the low quantum efficiency due to the low fill factor of quantum dots layer. Resonant cavity enhanced QDIP has been studied to increase the quantum efficiency. Different schemes of mirrors using free carrier plasma and distributed Bragg reflector are discussed. reprint
 

Page 1  (11 Items)