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Voltage-tunable dual-band Ge/Si photodetector operating in VIS and NIR spectral range

E. Talamas Simola, A. De Iacovo, J. Frigerio, A. Ballabio, A. Fabbri, G. Isella, and L. Colace

Open Access Open Access

Abstract

Extending and controlling the spectral range of light detectors is very appealing for several sensing and imaging applications. Here we report on a normal incidence dual band photodetector operating in the visible and near infrared with a bias tunable spectral response. The device architecture is a germanium on silicon epitaxial structure made of two back-to-back connected photodiodes. The photodetectors show a broad photoresponse extending from 390nm to 1600nm with the capability to electronically select the shorter (400-1100 nm) or the longer (1000-1600 nm) portion with a relatively low applied voltage. Devices exhibit peak VIS and NIR responsivities of 0.33 and 0.63 A/W, respectively, a low optical crosstalk (<-30dB), a wide dynamic range (>120dB) and, thanks to their low voltage operation, maximum specific detectivities of 7·1011cmHz1/2/W and 2·1010cmHz1/2/W in the VIS and NIR, respectively.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

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Figures (10)
Fig. 1
Fig. 1 Schematic representation of the principle of operation the back-to-back photodetector.

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Fig. 2
Fig. 2 (a) Schematic representation of the epitaxial stack. (b) Temperature profile during the post-growth thermal cycling.

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Fig. 3
Fig. 3 Band diagram of the sample in the region around the interface between silicon and germanium. The inset shows the band diagram of the full structure.

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Fig. 4
Fig. 4 SEM images of one of the processed devices in top view (a) and side view (b).

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Fig. 5
Fig. 5 40x40 µm2 scan of the surface of the sample.

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Fig. 6
Fig. 6 RSMs for the 004 (a) and 224 (b) reflections. The color scale represents the intensity measured as counts per seconds.

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Fig. 7
Fig. 7 (a) Current-voltage characteristic, (b) capacitance-voltage characteristic of the back-to-back photodiode.

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Fig. 8
Fig. 8 (a) Device spectral responses measured at VB = + 1V (blue) and at VB = −1V (red), (b) wavelength crosstalk defined according to Eq. (1).

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Fig. 9
Fig. 9 (a) Photocurrent-voltage characteristics measured at optical radiation at λ = 600 (blue) and λ = 1400nm (red), (b) voltage crosstalk defined according to Eq. (2).

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Fig. 10
Fig. 10 (a) Specific detectivity measured at VB = + 1V (blue) and at VB = −0.5V (red), (b) photocurrent versus optical intensity at λ = 633nm and λ = 1520nm.

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Equations (3)

Equations on this page are rendered with MathJax. Learn more.

C V 1 V 2 ( λ )=20log I ph ( λ, V 2 ) I ph ( λ, V 1 )
C λ 1 λ 2 ( V )=20log I ph ( V, λ 2 ) I ph ( V, λ 1 )
D * = R AB i n
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