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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 7 — Mar. 26, 2012
  • pp: 7608–7615
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Silicon-Germanium multi-quantum well photodetectors in the near infrared

Efe Onaran, M. Cengiz Onbasli, Alper Yesilyurt, Hyun Yong Yu, Ammar M. Nayfeh, and Ali K. Okyay  »View Author Affiliations


Optics Express, Vol. 20, Issue 7, pp. 7608-7615 (2012)
http://dx.doi.org/10.1364/OE.20.007608


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Abstract

Single crystal Silicon-Germanium multi-quantum well layers were epitaxially grown on silicon substrates. Very high quality films were achieved with high level of control utilizing recently developed MHAH epitaxial technique. MHAH growth technique facilitates the monolithic integration of photonic functionality such as modulators and photodetectors with low-cost silicon VLSI technology. Mesa structured p-i-n photodetectors were fabricated with low reverse leakage currents of ~10 mA/cm2 and responsivity values exceeding 0.1 A/W. Moreover, the spectral responsivity of fabricated detectors can be tuned by applied voltage.

© 2012 OSA

1. Introduction

The established silicon (Si) complementary metal-oxide semiconductor (CMOS) technology provides a low-cost platform and reproducible fabrication capabilities for on-chip optical and electronic signal processing. Integrated light detectors and modulators offer added functionality to modern integrated circuits (ICs). Compound semiconductor-based devices (e.g. InGaAs) enjoy high performance. Stringent market requirements drive the development of lower-cost and easier-to-integrate SiGe optoelectronic device technology. While compound semiconductor optoelectronic devices operate with relatively high performance, SiGe-based optoelectronic devices offer ease of processing and integration with electronics, low cost and strain tunability. Germanium is a promising semiconductor compatible with both CMOS and Group III-V technologies and it is sensitive at standard telecommunication bands (C-band, L-band) where Si is transparent [1

1. J. Mathews, R. Roucka, J. Xie, S.-Q. Yu, J. Menéndez, and J. Kouvetakis, “Extended performance GeSn/Si(100) p-i-n photodetectors for full spectral range telecommunication applications,” Appl. Phys. Lett. 95(13), 133506 (2009). [CrossRef]

]. Using Si as a platform, growth of Ge-on-Si enables the low-cost integration of optoelectronics and CMOS technologies. Monolithic integration of optoelectronic devices on-chip with higher density and increased functionality thus becomes possible.

Direct growth of Ge on Si is challenging due to the mismatch of lattice parameters and thermal expansion coefficients of Ge and Si, causing threading dislocations to propagate from the interface and leading to poor device performance or complete device failure. Recently, Nayfeh and associates developed multiple hydrogen annealing heteroepitaxy (MHAH) that enables low dislocation-density Ge growth on Si [2

2. A. M. Nayfeh, C. O. Chui, K. C. Saraswat, and T. Yonehara, “Effects of hydrogen annealing on heteroepitaxial-Ge layers on Si: surface roughness and electrical quality,” Appl. Phys. Lett. 85(14), 2815–2817 (2004). [CrossRef]

5

5. H.-Y. Yu, S. Ren, W. S. Jung, A. K. Okyay, D. A. B. Miller, and K. C. Saraswat, “High-efficiency p-i-n photodetectors on selective-area-grown Ge for monolithic integration,” IEEE Electron Device Lett. 30(11), 1161–1163 (2009). [CrossRef]

].

2. Device fabrication

MQW samples were patterned in disc shaped mesas using standard UV photolithography, etched with SF6 gas at a rate of 175 nm/min down to highly doped Si substrate to become circular mesa structures for detector mode operation. Mesa structures were chosen with respect to other electrode topologies (i.e. planar interdigitated electrodes) since (i) vertical photocurrent collection isolates the photodetector from remaining surface of substrate and thus reduces surface leakage current and (ii) fringing fields are mostly avoided and almost all of the E-field bias participates into charge separation and collection. A 200-nm-thick conformal Si3N4 layer was deposited with plasma enhanced chemical vapor deposition (PECVD) for passivation of surface and sidewalls and as an antireflection coating. A thin (~10 nm) Ti adhesion layer was evaporated. Finally, Al was thermally evaporated on Ti to become the 200 nm thick top and bottom electrodes. Figure 5(a)
Fig. 5 (a) Scanning electron microscope (SEM) image of the completed p-i-n optical detector. The lower inset is an illustration of the device cross section, (b) Measured photodetector dark current as a function of mesa area at different bias voltages.
shows the scanning electron microscope (SEM) image of the completed devices.

3. Optoelectronic characterization

Current output (I-V) and responsivity of these photodetectors as a function of voltage bias were measured to test the performance of the low temperature grown mesa shaped MQW photodetectors. Figure 5(b) shows the measured reverse leakage current with respect to mesa area. Linear relation between leakage current and mesa area indicates that the bulk leakage dominates surface leakage and the bulk component essentially determines total leakage. Responsivity of 0.1 A/W was measured at 1310 nm and 0V bias for the device with 120 µm mesa diameter. Table 2

Table 2. Reported Dark Current Density and Responsivity Values from Literature

table-icon
View This Table
| View All Tables
shows the best-reported Si-Ge based p-i-n and an extremely efficient MSM photodetector responsivity performances and corresponding parameters.

For the devices with 20 µm and 120 µm mesa diameters, reverse leakage current of 32 nA and 1.27 μA at −1V bias was measured, respectively, which correspond to ~10 mA/cm2 leakage current density. This value is comparable with reported values for p-i-n photodetectors in the literature, listed in Table 2. The bulk current dominates the total dark current verified by the linear relation between the dark current density obtained from different mesa area devices, which is attributed to low surface leakage. Photocurrent data was acquired with chopped xenon light bulb source with a 12.5 cm monochromator with a 600 lines mm−1grating, and a lock-in amplifier. Figure 6
Fig. 6 Measured spectral responsivity of fabricated devices with a mesa diameter of 80 µm.
plots the acquired spectral response of a 80-μm-diameter device for different applied reverse bias voltages. Measured responsivity values in excess of 100 mA/W are obtained in the 1300-1600 nm spectral range. The responsivity could be further increased by MQW layer thickness, which may limit device speed. Assuming a fully depleted intrinsic layer (300 nm), carrier transit time would be in the order of a few picoseconds. For devices with areas less than 100 square microns, the RC time constant is estimated to be less than a picosecond (50 Ω resistance and 0.35 fF/cm2 detector capacitance per unit area), suggesting that device speed is limited by carrier transit time, though no measurements were performed to verify this claim. The spectral responsivity of the fabricated optical devices can be tuned by the applied reverse bias as shown for reverse bias voltages in Fig. 6. The absorption edge of the devices can be shifted by several tens of nanometers by applying few volts (<3 V) which is promising for low cost integration. It may be possible to use cavity or plasmonic resonance to increase the field intensity in the absorbing layer, to further improve device responsivity without limiting the carrier transit time.

In conclusion, mesa structured p-i-n photodetectors based on SiGe multi quantum well absorbing layers with voltage-tunable spectral response are experimentally demonstrated. Single crystal SiGe multi quantum well layers with low dislocation-density are grown on Silicon substrates by MHAH technique, enabling compatibility with III-V optoelectronics and Silicon VLSI technology. Nanostructural characterization indicates that high quality quantum well layers are formed. Experimental results from fabricated photodetector devices show moderate responsivity values of about 0.1 A/W and low dark current density of approximately 10 mA/cm2. In addition, voltage-tunable spectral response is also demonstrated. Integration of such voltage-tunable photodetectors with low cost Si technology is promising for added optical functionality for VLSI devices.

Acknowledgments

This work was supported by EU FP7 Marie Curie IRG Grant 239444, COST NanoTP, TUBITAK EEEAG Grants 108E163 and 109E044 and TUBITAK BIDEB.

References and links

1.

J. Mathews, R. Roucka, J. Xie, S.-Q. Yu, J. Menéndez, and J. Kouvetakis, “Extended performance GeSn/Si(100) p-i-n photodetectors for full spectral range telecommunication applications,” Appl. Phys. Lett. 95(13), 133506 (2009). [CrossRef]

2.

A. M. Nayfeh, C. O. Chui, K. C. Saraswat, and T. Yonehara, “Effects of hydrogen annealing on heteroepitaxial-Ge layers on Si: surface roughness and electrical quality,” Appl. Phys. Lett. 85(14), 2815–2817 (2004). [CrossRef]

3.

A. K. Okyay, A. M. Nayfeh, K. C. Saraswat, T. Yonehara, A. Marshall, and P. C. McIntyre, “High-efficiency metal-semiconductor-metal photodetectors on heteroepitaxially grown Ge on Si,” Opt. Lett. 31(17), 2565–2567 (2006). [CrossRef] [PubMed]

4.

O. Fidaner, A. K. Okyay, J. E. Roth, R. K. Schaevitz, Y.-H. Kuo, K. C. Saraswat, J. S. Harris, and D. A. B. Miller, “Ge–SiGe quantum-well waveguide photodetectors on silicon for the near-infrared,” IEEE Photon. Technol. Lett. 19(20), 1631–1633 (2007). [CrossRef]

5.

H.-Y. Yu, S. Ren, W. S. Jung, A. K. Okyay, D. A. B. Miller, and K. C. Saraswat, “High-efficiency p-i-n photodetectors on selective-area-grown Ge for monolithic integration,” IEEE Electron Device Lett. 30(11), 1161–1163 (2009). [CrossRef]

6.

S. B. Samavedam, M. T. Currie, T. A. Langdo, and E. A. Fitzgerald, “High-quality germanium photodiodes integrated on silicon substrates using optimized relaxed graded buffers,” Appl. Phys. Lett. 73(15), 2125–2127 (1998). [CrossRef]

7.

J. L. Liu, Z. Yang, and K. L. Wang, “Sb surfactant-mediated SiGe graded layers for Ge photodiodes integrated on Si,” J. Appl. Phys. 99(2), 024504 (2006). [CrossRef]

8.

M. Oehme, J. Werner, E. Kasper, M. Jutzi, and M. Berroth, “High bandwidth Ge p-i-n photodetector integrated on Si,” Appl. Phys. Lett. 89(7), 071117 (2006). [CrossRef]

9.

J. Liu, J. Michel, W. Giziewicz, D. Pan, K. Wada, D. D. Cannon, S. Jongthammanurak, D. T. Danielson, L. C. Kimerling, J. Chen, F. Ö. Ilday, F. X. Kärtner, and J. Yasaitis, “High-performance, tensile-strained Ge p-i-n photodetectors on a Si platform,” Appl. Phys. Lett. 87(10), 103501 (2005). [CrossRef]

10.

L. Colace, M. Balbi, G. Masini, G. Assanto, H.-C. Luan, and L. C. Kimerling, “Ge on Si p-i-n photodiodes operating at 10 Gbit/s,” Appl. Phys. Lett. 88(10), 101111 (2006). [CrossRef]

11.

S. Famà, L. Colace, G. Masini, G. Assanto, and H.-C. Luan, “High performance germanium-on-silicon detectors for optical communications,” Appl. Phys. Lett. 81(4), 586–588 (2002). [CrossRef]

12.

D. Ahn, C. Y. Hong, J. Liu, W. Giziewicz, M. Beals, L. C. Kimerling, J. Michel, J. Chen, and F. X. Kärtner, “High performance, waveguide integrated Ge photodetectors,” Opt. Express 15(7), 3916–3921 (2007). [CrossRef] [PubMed]

13.

L. Vivien, J. Osmond, J.-M. Fédéli, D. Marris-Morini, P. Crozat, J.-F. Damlencourt, E. Cassan, Y. Lecunff, and S. Laval, “42 GHz p.i.n Germanium photodetector integrated in a silicon-on-insulator waveguide,” Opt. Express 17(8), 6252–6257 (2009). [CrossRef] [PubMed]

14.

B. Li, G. Li, E. Liu, Z. Jiang, J. Qin, and X. Wang, “Monolithic integration of a SiGe/Si modulator and multiple quantum well photodetector for 1.55 μm operation,” Appl. Phys. Lett. 73(24), 3504–3505 (1998). [CrossRef]

15.

Y.-H. Kuo, Y. K. Lee, Y. Ge, S. Ren, J. E. Roth, T. I. Kamins, D. A. B. Miller, and J. S. Harris, “Strong quantum-confined Stark effect in germanium quantum-well structures on silicon,” Nature 437(7063), 1334–1336 (2005). [CrossRef] [PubMed]

16.

D. Miller, D. Chemla, T. Damen, A. Gossard, W. Wiegmann, T. Wood, and C. Burrus, “Band-edge electroabsorption in quantum well structures: the quantum-confined Stark effect,” Phys. Rev. Lett. 53(22), 2173–2176 (1984). [CrossRef]

17.

D. A. B. Miller, D. S. Chemla, T. C. Damen, A. C. Gossard, W. Wiegmann, T. H. Wood, and C. A. Burrus, “Electric field dependence of optical absorption near the band gap of quantum-well structures,” Phys. Rev. B Condens. Matter 32(2), 1043–1060 (1985). [CrossRef] [PubMed]

18.

C. Chen, B. Yu, J. Liu, and Q. Dai, “Structural characteristics of SiGe/Si materials investigated by Raman spectroscopy,” Met. Mater. Int. 11(4), 279–283 (2005). [CrossRef]

19.

J. Olivares, P. Martin, A. Rodriguez, J. Sangrador, J. Jimenez, and T. Rodríguez, “Raman spectroscopy study of amorphous SiGe films deposited by low pressure chemical vapor deposition and polycrystalline SiGe films obtained by solid-phase crystallization,” Thin Solid Films 358(1–2), 51–56 (2000). [CrossRef]

20.

H.-C. Luan, K. Wada, L. C. Kimerling, G. Masini, L. Colace, and G. Assanto, “High efficiency photodetectors based on high quality epitaxial germanium grown on silicon substrates,” Opt. Mater. 17(1-2), 71–73 (2001). [CrossRef]

21.

P. R. Bandaru, S. Sahni, E. Yablonovitch, J. Liu, H.-J. Kim, and Y.-H. Xie, “Fabrication and characterization of low temperature (<450 °C) grown p-Ge/n-Si photodetectors for silicon based photonics,” Mater. Sci. Eng. B 113(1), 79–84 (2004). [CrossRef]

22.

L. Colace, P. Ferrara, G. Assanto, D. Fulgoni, and L. Nash, “Low dark-current germanium-on-silicon near-infrared detectors,” IEEE Photon. Technol. Lett. 19(22), 1813–1815 (2007). [CrossRef]

OCIS Codes
(160.2100) Materials : Electro-optical materials
(230.5160) Optical devices : Photodetectors
(230.5590) Optical devices : Quantum-well, -wire and -dot devices
(230.4205) Optical devices : Multiple quantum well (MQW) modulators

ToC Category:
Detectors

History
Original Manuscript: January 3, 2012
Revised Manuscript: February 19, 2012
Manuscript Accepted: February 27, 2012
Published: March 19, 2012

Virtual Issues
Vol. 7, Iss. 5 Virtual Journal for Biomedical Optics

Citation
Efe Onaran, M. Cengiz Onbasli, Alper Yesilyurt, Hyun Yong Yu, Ammar M. Nayfeh, and Ali K. Okyay, "Silicon-Germanium multi-quantum well photodetectors in the near infrared," Opt. Express 20, 7608-7615 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-7-7608


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References

  1. J. Mathews, R. Roucka, J. Xie, S.-Q. Yu, J. Menéndez, J. Kouvetakis, “Extended performance GeSn/Si(100) p-i-n photodetectors for full spectral range telecommunication applications,” Appl. Phys. Lett. 95(13), 133506 (2009). [CrossRef]
  2. A. M. Nayfeh, C. O. Chui, K. C. Saraswat, T. Yonehara, “Effects of hydrogen annealing on heteroepitaxial-Ge layers on Si: surface roughness and electrical quality,” Appl. Phys. Lett. 85(14), 2815–2817 (2004). [CrossRef]
  3. A. K. Okyay, A. M. Nayfeh, K. C. Saraswat, T. Yonehara, A. Marshall, P. C. McIntyre, “High-efficiency metal-semiconductor-metal photodetectors on heteroepitaxially grown Ge on Si,” Opt. Lett. 31(17), 2565–2567 (2006). [CrossRef] [PubMed]
  4. O. Fidaner, A. K. Okyay, J. E. Roth, R. K. Schaevitz, Y.-H. Kuo, K. C. Saraswat, J. S. Harris, D. A. B. Miller, “Ge–SiGe quantum-well waveguide photodetectors on silicon for the near-infrared,” IEEE Photon. Technol. Lett. 19(20), 1631–1633 (2007). [CrossRef]
  5. H.-Y. Yu, S. Ren, W. S. Jung, A. K. Okyay, D. A. B. Miller, K. C. Saraswat, “High-efficiency p-i-n photodetectors on selective-area-grown Ge for monolithic integration,” IEEE Electron Device Lett. 30(11), 1161–1163 (2009). [CrossRef]
  6. S. B. Samavedam, M. T. Currie, T. A. Langdo, E. A. Fitzgerald, “High-quality germanium photodiodes integrated on silicon substrates using optimized relaxed graded buffers,” Appl. Phys. Lett. 73(15), 2125–2127 (1998). [CrossRef]
  7. J. L. Liu, Z. Yang, K. L. Wang, “Sb surfactant-mediated SiGe graded layers for Ge photodiodes integrated on Si,” J. Appl. Phys. 99(2), 024504 (2006). [CrossRef]
  8. M. Oehme, J. Werner, E. Kasper, M. Jutzi, M. Berroth, “High bandwidth Ge p-i-n photodetector integrated on Si,” Appl. Phys. Lett. 89(7), 071117 (2006). [CrossRef]
  9. J. Liu, J. Michel, W. Giziewicz, D. Pan, K. Wada, D. D. Cannon, S. Jongthammanurak, D. T. Danielson, L. C. Kimerling, J. Chen, F. Ö. Ilday, F. X. Kärtner, J. Yasaitis, “High-performance, tensile-strained Ge p-i-n photodetectors on a Si platform,” Appl. Phys. Lett. 87(10), 103501 (2005). [CrossRef]
  10. L. Colace, M. Balbi, G. Masini, G. Assanto, H.-C. Luan, L. C. Kimerling, “Ge on Si p-i-n photodiodes operating at 10 Gbit/s,” Appl. Phys. Lett. 88(10), 101111 (2006). [CrossRef]
  11. S. Famà, L. Colace, G. Masini, G. Assanto, H.-C. Luan, “High performance germanium-on-silicon detectors for optical communications,” Appl. Phys. Lett. 81(4), 586–588 (2002). [CrossRef]
  12. D. Ahn, C. Y. Hong, J. Liu, W. Giziewicz, M. Beals, L. C. Kimerling, J. Michel, J. Chen, F. X. Kärtner, “High performance, waveguide integrated Ge photodetectors,” Opt. Express 15(7), 3916–3921 (2007). [CrossRef] [PubMed]
  13. L. Vivien, J. Osmond, J.-M. Fédéli, D. Marris-Morini, P. Crozat, J.-F. Damlencourt, E. Cassan, Y. Lecunff, S. Laval, “42 GHz p.i.n Germanium photodetector integrated in a silicon-on-insulator waveguide,” Opt. Express 17(8), 6252–6257 (2009). [CrossRef] [PubMed]
  14. B. Li, G. Li, E. Liu, Z. Jiang, J. Qin, X. Wang, “Monolithic integration of a SiGe/Si modulator and multiple quantum well photodetector for 1.55 μm operation,” Appl. Phys. Lett. 73(24), 3504–3505 (1998). [CrossRef]
  15. Y.-H. Kuo, Y. K. Lee, Y. Ge, S. Ren, J. E. Roth, T. I. Kamins, D. A. B. Miller, J. S. Harris, “Strong quantum-confined Stark effect in germanium quantum-well structures on silicon,” Nature 437(7063), 1334–1336 (2005). [CrossRef] [PubMed]
  16. D. Miller, D. Chemla, T. Damen, A. Gossard, W. Wiegmann, T. Wood, C. Burrus, “Band-edge electroabsorption in quantum well structures: the quantum-confined Stark effect,” Phys. Rev. Lett. 53(22), 2173–2176 (1984). [CrossRef]
  17. D. A. B. Miller, D. S. Chemla, T. C. Damen, A. C. Gossard, W. Wiegmann, T. H. Wood, C. A. Burrus, “Electric field dependence of optical absorption near the band gap of quantum-well structures,” Phys. Rev. B Condens. Matter 32(2), 1043–1060 (1985). [CrossRef] [PubMed]
  18. C. Chen, B. Yu, J. Liu, Q. Dai, “Structural characteristics of SiGe/Si materials investigated by Raman spectroscopy,” Met. Mater. Int. 11(4), 279–283 (2005). [CrossRef]
  19. J. Olivares, P. Martin, A. Rodriguez, J. Sangrador, J. Jimenez, T. Rodríguez, “Raman spectroscopy study of amorphous SiGe films deposited by low pressure chemical vapor deposition and polycrystalline SiGe films obtained by solid-phase crystallization,” Thin Solid Films 358(1–2), 51–56 (2000). [CrossRef]
  20. H.-C. Luan, K. Wada, L. C. Kimerling, G. Masini, L. Colace, G. Assanto, “High efficiency photodetectors based on high quality epitaxial germanium grown on silicon substrates,” Opt. Mater. 17(1-2), 71–73 (2001). [CrossRef]
  21. P. R. Bandaru, S. Sahni, E. Yablonovitch, J. Liu, H.-J. Kim, Y.-H. Xie, “Fabrication and characterization of low temperature (<450 °C) grown p-Ge/n-Si photodetectors for silicon based photonics,” Mater. Sci. Eng. B 113(1), 79–84 (2004). [CrossRef]
  22. L. Colace, P. Ferrara, G. Assanto, D. Fulgoni, L. Nash, “Low dark-current germanium-on-silicon near-infrared detectors,” IEEE Photon. Technol. Lett. 19(22), 1813–1815 (2007). [CrossRef]

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