Monolithically Integrated Dual-Band Quantum Well Infrared Photodetector
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G.E. Stillman, A.P. Curtis, S. Kim, L.J. Chou, P.J. Mares, M. Feng, K.C. Hseih, S.L. Chuang, S.G. Bishop, and Y.C. Chang Microelectronics Laboratory, Department of Electrical Engineering, Department of Physics & Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801 H.C. Liu Institute of Microstructural Sciences, National Research Council, Canada KIA 0R6 W.I. Wang Department of Electrical Engineering, Columbia University, New York, NY 11007
ABSTRACT A monolithic quantum well infrared photodetector (QWIP) structure has been presented that is
suitable for dual bands in the two atmospheric transmission windows of 3 - 5.3 jim and 7.5 - 14jtm, respectively. The proposed structure employs dual stacked, strain InGaAs/A1GaAs and latticematched GaAs/A 1GaAs quantum well infrared photodetector for mid wavelength and long wavelength detection. The response peak of the strain InGaAs/AlGaAs quantum well is at 4.9 jtm and the lattice-matched GaAs/AlGaAs is at 10.5gm; their peak sensitivities are in the spectral regions of 3 - 5.3jim and 7.5 - 14gtm. The peak responsivity when the dual-band QWIP is biased at 5 Volts is -0.065A/W at 4.9gtm and -0.006A/W at 10.5im ; at this voltage the dual-band QWIP is more sensitive at the shorter wavelengths due to its larger impedance thus exhibiting wavelength tunability characteristics with bias. Additionally, single colored 4.9 and 10.5jm QWIPs were fabricated from the dual-band QWIP structure to study the bias-dependent behavior and also to understand the effects of growing the strain layer InGaAs/AlGaAs QWIP on top of the lattice-matched GaAs/ AlGaAs QWIP. In summary, two stack dual-band QWIPs using GaAs/A1GaAs and strained InGaAs/ A1GaAs multiquantum wells have been demonstrated with peak spectral sensitivities in the spectral region of 3 - 5.3jim and 7.5 - 14jtm. Also, the voltage tunable dual-band detection have been realized for this kind of QWIP structure.
205 Mat. Res. Soc. Symp. Proc. Vol. 484 ©1998 Materials Research Society
INTRODUCTION Multispectral infrared detectors would be highly beneficial for a variety of applications such as guidance, surveillance, detection, tracking, imaging and monitoring [1,2]. Dual-band detection in the mid-IR and far-IR atmosphere window have been performed using HgCdTe photodiodes or photoconductive devices [3,4]. Compared with HgCdTe, the quantum well infrared photodetector (QWIP) based on intersubband transitions in GaAs/AlGaAs, InGaAs/AlInAs, InGaAs/InP and InGaAs/InGaAsP superlattices offer greater potential as infrared detectors than HgCdTe because they are easier to grow with high quality and uniformity [5,6,7,8,9,10]. In all cases its detection wavelength and thus the relevant energy bands are chosen prior to growth, and the layer structures are designed accordingly. Two or multiple color QWIPs have recently been demonstrated [ 11,12]. The structures of the dual-color QWIPs include multi-stack structures [13], symmetric [14], and asymmetric [ 15,16] quantum well structures. However, the operation wind
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