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Hengyang Photodetector

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Hengyang Photodetector
17
Photodetector on Silicon Heng Yang
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Page 1: Hengyang Photodetector

Photodetector on Silicon

Heng Yang

Page 2: Hengyang Photodetector

Outline

• Introduction• Si Photodetector in 770 ~ 850 nm

Range• IR Schottky barrier photodetector

Page 3: Hengyang Photodetector

Introduction• Essentially - p-n diode un

der the reverse bias• Operate in the photocond

uctive mode• Main usage - for the conv

ersion of the optical signal

• works at 0.3 - 1.1 µm (peak responsivity at 0.8 µm).

Page 4: Hengyang Photodetector

Si Photodetector in 770 ~ 850 nm Range

• Optical communication range.• Absorption length for Si: 10 ~ 15 m. • Requirements: High responsivity and Fast?• pn, pin and msm.

p

n

Depletion region J = Jdrfit + Jdiff

Page 5: Hengyang Photodetector

Interdigitated Electrode

Interdigitated electrodes are often used to increase the active region area while optimizing the electric fields in the carrier collection region.

Electrode can either be P+/N+ or just metal.

Page 6: Hengyang Photodetector

Silicon Lateral Trench Photodetector

Min Yang, Kern Rim, Dennis L. Rogers, et al., IEEE ELECTRON DEVICE LETTERS, VOL. 23, NO. 7, JULY 2002

Finger space = 3.3 mTrench depth = 8 mFinger size = 0.35 m For =845 nm, BW=1.5 GHz, Responsivity = 0.47 A/W at 5V

Page 7: Hengyang Photodetector

MSM Photodetector by Trench Formation

Jacob Y. L. Ho and K. S. Wong, IEEE Photonics Technology Letters, 8(8), 1996

For = 790 nm, BW = 2.2 GHz, Responsivity = 0.14 A/W @ 5V

Page 8: Hengyang Photodetector

Resonant-Cavity-Enhanced High-Speed Si Photodetector

J. D. Schaub, R. Li, C. L. Schow, J. C. Campbell, G. W. Neudeck, and J. Denton,IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 11, NO. 12, DECEMBER 1999

Three pair of quarter wavelength

SiO2 and polysilicon at bottom (L

PCVD).Etched seed window.

SiO2 Side-wall to prevent defects

at the edge of poly.RPCVD Si.Two pairs of ZnSe-MgF on top (evaporated).

Page 9: Hengyang Photodetector

Photodetector on SOI

• Thin active layer, and small finger space result in high speed.

• Device with 100nm active layer and 100nm finger space was made. =780 nm BW=140 GHz, responsivity=5.7 mA/W @ 5V.

M. Y. Liu, E. Chen, and S. Y. Chou, Appl. Phys. Lett. 65 (7), 15 August 1994

Silicon

Silicon dioxide

Page 10: Hengyang Photodetector

IR Schottky Barrier (SB) Photodetector

300,000 PtSi/p-Si Schottky barrier IR detector focal plane arrays have been developed and used on Air Force B-52

Page 11: Hengyang Photodetector

IR Schottky Barrier Photodetector

Internal Photoemission Intrinsic Mechanism

BC q

24.1

Page 12: Hengyang Photodetector

Issues

• High dark current, has to operate at low temperature (40 ~ 80 K).

• Low quantum efficiency (QE).

2

1

2

11124.1

C

B ChqhCQE

High C gives high QE. In order to expand the spectrum, efforts were made to decrease the barrier height.

Page 13: Hengyang Photodetector

Fowler Plot

• The dark current is thermionic limited. It is given by:

• A** is Richardson constant

• By plotting J0/T2 vs 1/T, qcan be obtained from the slope.

)/exp(** 20 kTqTAJ B

Page 14: Hengyang Photodetector

PtSi/p-Si Schottky Barrier

• Second lowest barrier height (0.22eV). More than IrSi (0.16eV).

• Low expense.• Compatible with standard IC process.• Stable.• Good uniformity over large area.• Good growth and etching selectivity.

Page 15: Hengyang Photodetector

PtSi Schottky-Barrier Infrared Focal Plane Arrays

Masafumi Kimata, Tatsuo Ozaki, Natsuro Tsubouchi and Sho Ito, Proceeding of SPIE, 1998

Page 16: Hengyang Photodetector

SBD with a shallow P+ layer• PtSi/p-Si, qB = 0.22 eV, c = 5.

6 m. (M. Kimata, M. Denda et. al, Inter. J. of Infrared and millimeter waves, 6(10), 1985)

• PtSi/p+ (100 ~ 300 nm)/p-Si, qB < 0.22 eV, with hole tunneling, c = 7 m. (CY Wei, W. Trantraporn, W. Katz and G. Smith, 93, 1981)

• PtSi/p+ (1nm)/p-Si, qB = 0.057 eV, c = 22 m. (TL Lin, JS Park et. al, Appl. Phys. Lett. 62(25), 1993)

TL Lin, JS Park et al.Appl. Phys. Lett. 62(25), 1993

Page 17: Hengyang Photodetector

Porous Silicon (PS) Schottky Barrier Detector

• The modification was made just to make the PtSi on top of the PS in stead of Si. Pt was deposited by electrodeposition

• The cut-off wavelength of 7 m was reported.

• QE ~ 10% @ 7 m • Random orientation of the

junctions increase the number of holes that can be injected into Si.

Farshid Raissi and Mansoor Mohtashami Far, IEEE Sensors Journal, 2 (5) 2002


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