Tailoring mid- and long-wavelength dual response of InAs quantum-dot infrared photodetectors using InxGa1−xAs capping layers

Abstract

We report on the tailoring of detection bands of InAs quantum-dot infrared photodetectors ͑QDIPs͒ using In x Ga 1Ϫx As capping layers and on the realization of voltage-tunable two-color QDIPs for mid-wavelength infrared ͑MWIR͒ and long-wavelength infrared ͑LWIR͒ detection. QDIPs having 2.0 ML InAs QDs capped by 20 ML In 0.15 Ga 0.85 As layer show bias-dependent photocurrent peak positions in the LWIR regime (ϳ8 -9 m) which are redshifted with respect to those (ϳ5 -7 m) in the counterpart QDIPs without In x Ga 1Ϫx As capping layers. QDIPs having 2.5 ML InAs QDs capped by a 30 ML In 0.15 Ga 0.85 As layer have a bimodal QD size distribution and show voltage-tunable MWIR (ϳ5.5-6 m) and LWIR (ϳ9 -11 m) photoresponse. At low bias, MWIR photoresponse is dominant whereas with increasing bias, the LWIR photoresponse becomes dominant.

High detectivity InAs quantum dot infrared photodetectors

“…͓DOI: 10.1063/1.1719259͔ Quantum well infrared photodetectors ͑QWIPs͒ have been the subject of extensive research efforts for infrared imaging applications. [5][6][7][8][9][10][11][12][13][14] Recently, QDIPs with single or dual peak photoresponses between 3-14 m have been reported, [5][6][7][8][9][10][11][12][13][14] among which the highest detectivities, D*, are 3ϫ10 9 ͑at 100 K͒, 10 10 , 3ϫ10 9 , 5ϫ10 9 , and 2 ϫ10 8 cm Hz 1/2 /W for 3.72, 6.2, 7.2, 8.3, and 13 m photoresponses at 77 K, respectively. The quantum dot based infrared photodetector ͑QDIP͒ is an alternative to QWIPs because the QDIPs, owing to the three-dimensional quantum confinement of the carriers in quantum dots, are inherently sensitive to normal incident radiation.…”

Voltage-controllable multiwavelength InAs quantum-dot infrared photodetectors for mid- and far-infrared detection

“…Figure 2 shows the spectral response and illustrates the bias-controllable multicolor characteristic. At low negative bias, the main photoresponse peak occurred at 5.5 m. This is due to the fact that the lower electron states in the larger QDs, whose intraband transitions contribute to the photoresponse of the 5.5 m peak, 13,14 are partially occupied; the small QDs, whose intraband transitions contribute to the photoresponse of the 8.9 m peak, [13][14][15] are relatively unoccupied. This results from the lower electron ground state energy ͑measured with respect to the GaAs conduction band edge͒ of larger QDs.…”

“…Most importantly, the three-dimensional confinement of electrons in the QD permits QDIPs to operate in the normal incidence mode, unlike n-type QWIPs which are not sensitive to radiation that is incident perpendicular to the quantum wells. 1 Recently, we reported a bias-controllable dual-wavelength photoresponse 13,14 in a QDIP structure that incorporated InAs QD layers with two different QD size distributions. In this article we report on the photodetector characteristics of this structure.…”

“…This results from the lower electron ground state energy ͑measured with respect to the GaAs conduction band edge͒ of larger QDs. 13,14 With increasing bias, the dark current increases, which results in increasing occupation of the electron ground states of the small QDs. The photoresponse for the 8.9 m peak is observed when the applied bias is greater than Ϯ0.2 V. We hypothesize that the gain of the photoexcited electrons from the small QDs increases more rapidly with bias than that of the large QDs.…”

Intraband and interband photocurrent spectroscopy and induced dipole moments of InAs/GaAs(001) quantum dots in n–i–n photodetector structures

“…The ground state occupation of the QDs in the n -i(QDs) -n configuration is examined and used to assign observed intraband transitions. The experimental results on long-wavelength In x Ga 1Ϫx As/GaAs QDIPs with n -n -n 3-10 and n -i -n configurations [11][12][13][14] show promise. Stark shift in interband photocurrent spectroscopy reveals the presence and direction of interband transition induced dipoles, making this study the first to determine both intra-and interband dipoles in the same ensemble of QDs.…”