Spectral Response Modification Of Quantum Well Infrared Photodetector By Quantum Well Intermixing
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Spectral Response Modification Of Quantum Well Infrared Photodetector By Quantum Well Intermixing J. C. Shin1, W. J. Choi1*, I. K. Han1, Y. J. Park1, J. I. Lee1, E. K. Kim2, H. J. Kim3, J. W. Choi3 1
Nano-Device Research Center, Korea Institute of Science and Technology P.O.Box 131 Cheongryang, Seoul 130-650, Korea 2 3
Dept. of Physics, Hanyang University, Seoul 133-751, Korea
Dept. of Physics, Kyunghee University, Yongin 449-701, Korea *
E-mail: [email protected], Tel: +82-958-5783, Fax:+82-2-958-5709
ABSTRACT We have studied the change of the spectral response in a quantum well infrared photodetector (QWIP) by using the impurity-free vacancy disordering (IFVD) to change the bandgap of the GaAs/AlGaAs multiple quantum well absorption layer. IFVD process has been carried out with PECVD-grown SiO2 capping on the MOCVD-grown QWIP structure, whose absorption region consists of 25 periods of 3.6nm thick Si-doped GaAs well and 50nm thick Al0.24Ga0.76As barrier. The PL peak of MQW decreased with the increase of annealing temperature and time from 802 nm to 700 nm at 15 K. The fabricated QWIP whose absorption region was intermixed at 850 oC by IFVD technique showed the maximum change in spectral response from 8 to 10 um when compared to a QWIP without intermixing. This result implies that the intermixing technology can be used to make multicolor QWIP without growing multiple IR absorption regions. INTRODUCTION The detection of thermal radiation is very important for the application of Infrared (IR) communication, medical treatment, detecting gas leak and security of industrial equipment [1]. For this purpose, HgCdTe material system has been widely studied and used to detect IR radiation. Though the HgCdTe material system provides high quantum efficiency and detectivity, through a band-to-band transition, in the IR detection, this material system shows low stability and low uniformity in a whole wafer, which gives a limitation to fabricate a stable IR detector array. Since the bandgap energy of III-V compound semiconductor is larger than the photon energy whose wavelength is longer than 2 µm, IR detection is impossible through band-to-band
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transition for the wavelength longer than 2 µm with III-V compound semiconductor. However, since the energy difference between inter-subbands of quantum well is well matched to the energy of IR photon, IR detection is possible with III-V compound semiconductor. West at al. has reported first quantum well infrared photodetector (QWIP) utilizing inter-subband transition in GaAs/AlGaAs quantum well (QW) in 1985 [2]. Since QWIP provides high detectivity, quick response, high stability, and cost-effective fabrication with the III-V compound semiconductor device fabrication technology, many researchers have studied QWIP [3-8]. Two-color QWIP for dual band IR detection has wide applications in remote sensing. Recently, Gunaplla et al. proposed two-color QWIP by using stacked two different QW structures for dual band IR detection [8]. But the fabrication of this type of two
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