Photovoltaic Ge/Si quantum dot detectors operating in the mid-wave atmospheric window (3 to 5 μ m)

Abstract

Ge/Si quantum dots fabricated by molecular-beam epitaxy at 500°C are overgrown with Si at different temperatures Tcap, and effect of boron delta doping of Si barriers on the mid-infrared photoresponse was investigated. The photocurrent maximum shifts from 2.3 to 3.9 μm with increasing Tcapfrom 300°C to 750°C. Within the sample set, we examined devices with different positions of the δ-doping layer with respect to the dot plane, different distances between the δ-doping layer and the dot plane d, and different doping densities pB. All detectors show pronounced photovoltaic behavior implying the presence of an internal inversion asymmetry due to the placing dopants in the barriers. The best performance was achieved for the device with Tcap = 600°C, pB = 12 × 1011cm−2, and d = 5 nm in a photovoltaic regime. At a sample temperature of 90 K and no applied bias, a responsivity of 0.83 mA/W and detectivity of 8 × 1010 cm Hz1/2/W at λ = 3.4 μm were measured under normal incidence infrared radiation.

Broadband Ge/SiGe quantum dot photodetector on pseudosubstrate

“…At zero bias, no signal is observed implying the device operates in a photoconductive mode [22], and at biases just above 3.5 V, the signal becomes too noisy to detect PC. Ge/SiGe QDIP is of wide detection window with the cutoff wavelength of about 12 μ m instead of 5 to 6 μ m for Ge/Si QDIPs of similar device structure [11]. Since the sample in FTIR experiments is simultaneously exposed to a wide range of photon energies, the spectra may display additional transitions due to two-photon processes [9].…”

“…Thus, we conclude that the observed redshift is a result of smaller effective valence band offset at the Ge/Si 1− x Ge x interface. By an analogy with the behavior of Ge/Si QDIPs [11], the near-infrared response at λ <2 μ m is ascribed to the interband transitions between the electrons in the δ valleys of SiGe layers and the holes at the Γ point of Ge QDs. The mid-infrared signal at λ >3 μ m is associated with the hole intraband transitions which involve the dot bound states.…”

“…The photoresponse of Ge/Si heterostructures with QDs in the mid-wave atmospheric window was observed by several groups [6-10] and attributed to the transitions from the hole states bound in Ge QDs to continuum states of the Si matrix. Recently, we have reported on the photovoltaic operation of ten-period Ge/Si(001) QDIPs with Johnson noise-limited detectivity as high as 8×10 10 cm Hz 1/2 /W measured at photon wavelength ( λ )=3.4 μ m and at 90 K under normal incidence IR radiation [11]. The cutoff wavelength at the low energy side of the responsivity of such QDIPs was limited to about 5 μ m.…”

Плазмонное усиление поля в фотоприемниках среднего ИК-диапазона на базе квантовых точек Ge/Si с различной толщиной активной зоны

“…3) Контролируя размер и состав КТ Ge/Si, можно управлять спектральным составом чувствительности детекторов [4][5][6][7][8].…”

Разрывы валентной зоны в напряженных слоях SiGeSn/Si с различным содержанием олова

“…На преодоление указанных ограничений тратится много усилий, и при-меняются различные подходы, такие как использование сплавов элементов IV группы таблицы Менделеева и наноструктур на их основе. В разные годы предлага-лось рассматривать гетероструктуры GeSi с квантовыми точками (КТ) [1][2][3][4]. Данный подход дал определенные результаты, но из-за малой плотности квантовых точек не удается получить значительную величину квантового выхода в фотоприемных устройствах.…”