Long-wavelength quantum structure infrared photodetectors

Abstract

Long-wavelength infrared photodetectors using quantum structure including quantum-wells (QW) and quantum-dots (QD) were demonstrated. The selection rule of n-type QW structure prevents the quantum well infrared photodetector (QWIP) from absorbing normally incident light, which initiate the study on the methods for overcoming the selection rule. First, the conventional waveguide-type GaAs/AlGaAs QWIP was fabricated. The QWIP contained 45° polished edge upon which the light impinged. Second, multiquantum well grown on the V-groove-substrate was used to fabricate normal incidence GaAs/AlGaAs QWIP. The above two QWIPs showed the photoconductive signal with the peak wavelength of 9.2㎛. Third, the performances of (111) and (100) p-type GaAs/AlGaAs QWIP were theoretically studied by 4×4 Kohn-Luttinger Hamiltonian. The p-type QWIP using intervalence-subband transitions respond with normally indident light due to the s- and p-band mixing. The quantum efficiency of the (111) p-type QWIP was ~67% of that of the (100) p-type QWIP. Nevertheless, the detectivity of the (111) p-type QWIP was~30% larger than that of the (100) p-type QWIP. This was because of the extremely low dark current due to the heavier heavy hole of (111) QWIP. The modulation-doped lateral transport quantum dot infrared photodetector (LAT-QDIP) which contains five stacks of InAs/GaAs QDs underdneath the GaAs/AlGaAs hetero interface was demonstrated with the peak wavelength of ~10㎛. The LAT-QDIP has three superiorities compared to conventional n-i-n diode structure QDIP which utilizes vertical transport. First, the LAT-QDIP has low noise mechanism which is achieved by decoupling the transport region from the noisy QD region. Furthermore, it is well known that the two-dimensional transport channel has very low noise. Second, the LAT-QDIP has extremely low dark current. This is because the electrons captured in QDs can hardly be thermalized due to the high barrier of QDs which have discrete energy level an...