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Characterization of a Geiger-mode Avalanche Photodiode. Chris Maloney May 10, 2011. Project Objectives. To extract key parameters that will allow for effective and efficient operation of a Geiger-mode avalanche photodiode array in a LIDAR imaging system. Project Goals. Extract key parameters
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Characterization of a Geiger-mode Avalanche Photodiode Chris Maloney May 10, 2011
Project Objectives • To extract key parameters that will allow for effective and efficient operation of a Geiger-mode avalanche photodiode array in a LIDAR imaging system Characterization of a Geiger-Mode APD C. Maloney
Project Goals • Extract key parameters • Breakdown voltage • Diode ideality factor • Series resistance • Dark count rate • Optimal bias for imaging • Number of traps present • Type of traps present Characterization of a Geiger-Mode APD C. Maloney
Applications • Avalanche photodiodes (APDs) are used for light detection and ranging (LIDAR) Color coded video of a Chevy van produced by Lincoln Lab LIDAR system Characterization of a Geiger-Mode APD C. Maloney
Applications • Altimetry • Measuring rainforest canopy • Measuring polar icecaps • Mapping celestial bodies • Mapping ocean topography • Autonomous Landing • Unmanned aircrafts • Landing on Mars • Landing on an asteroid (Image Credit: MOLA Science Team and G. Shirah, NASA GSFC Scientific Visualization Studio.) Characterization of a Geiger-Mode APD C. Maloney
Background • Lincoln Laboratory at MIT has fabricated a 32x32 array of Geiger-mode APDs for LIDAR imaging applications Characterization of a Geiger-Mode APD C. Maloney
Linear-mode vs. Geiger-mode • APDs can be operated in linear-mode or Geiger-mode • Geiger-mode provides much more sensitivity • Linear-mode can produce intensity images M Ordinary photodiode Linear-mode APD Geiger-mode APD 100 10 1 0 Breakdown Response to a photon ∞ I(t) M 1 (Image Credit: D.F Figer.) Characterization of a Geiger-Mode APD C. Maloney
Project Flowchart NO YES Characterization of a Geiger-Mode APD C. Maloney
System Design CAD camera part Fabricated camera Characterization of a Geiger-Mode APD C. Maloney
Front View Without the lens Characterization of a Geiger-Mode APD C. Maloney
Readout board integrated with camera View inside of camera Characterization of a Geiger-Mode APD C. Maloney
Detector integrated with readout board 32x32 APD array Readout board and detector are both from MIT’s Lincoln Laboratories Characterization of a Geiger-Mode APD C. Maloney
System Design Complete LIDAR system Characterization of a Geiger-Mode APD C. Maloney
Diode IV Testing • Shielded Probe Station • Agilent 4156B Parameter Analyzer • Noise Floor ~ 1 fA Characterization of a Geiger-Mode APD C. Maloney
Measured Reverse Diode Current vs. Voltage Breakdown Voltage = 28 V Dark Current = 0.1 pA Dark Current Density ~ 1 nA/cm2 All diodes across the wafer are uniform Characterization of a Geiger-Mode APD C. Maloney
Measured Forward Diode Current vs. Voltage Series resistance = 2 kΩ n = 1.0 No R/G region No R/G region implies number of traps are minimal Characterization of a Geiger-Mode APD C. Maloney
Gate Width Definition • The amount of time the detector is ready to detect a photon hν Gate Width Timing Gate Characterization of a Geiger-Mode APD C. Maloney
Measured Dark Count Rate vs. Gate Width Dark count rate should be constant Characterization of a Geiger-Mode APD C. Maloney
Dead Pixels Upper right corner is unresponsive due to low yielding bump-bonds Characterization of a Geiger-Mode APD C. Maloney
Measured Dark Count Rate vs. Gate Width – 9 by 8 array Dark count rate is constant and no longer decreasing Characterization of a Geiger-Mode APD C. Maloney
Measured Dark Count Rate vs. Bias Add ~5V to x-axis to account for cathode voltage Breakdown voltage is higher than breakdown extracted from IV curve Characterization of a Geiger-Mode APD C. Maloney
Afterpulsing Theory • Detector is armed and a laser pulse is detected • Detector cannot detect photons for tdead • Any carriers caught in traps will also discharge • Detector is armed • If tdead is shorter than the trap lifetime then the trap will discharge while the detector is armed and will result in a false event Afterpulse Laser-induced firing APD current APDbias Varm Timing gate tdead Characterization of a Geiger-Mode APD C. Maloney
Afterpulsing Model [1] λ – dark count rate Rdark – measured dark count rate without afterpulsing Pa – avalanche probability Nft – number of filled traps tdead – dead time τtrap – trap lifetime Characterization of a Geiger-Mode APD C. Maloney
Measured Afterpulsing • No afterpulsing seen • No traps • or • Trap lifetime • >500 μs Characterization of a Geiger-Mode APD C. Maloney
Acknowledgements • Rochester Imaging Detector Lab • Dr. Don Figer • John Frye • Dr. Joong Lee • Brandon Hanold • Kim Kolb • Microelectronic Engineering Department • Dr. Rob Pearson • Dr. Sean Rommel • Dr. Karl Hirschman • This work has been supported by NASA grant NNX08AO03G Characterization of a Geiger-Mode APD C. Maloney
References [1] K.E. Jensen, “Afterpulsing in Geiger-mode avalanche photodiodes for 1.06 μm wavelength” Lincoln Laboratory, MIT 2006. [2] D. Neamen, “An Introduction to Semiconductor Devices” McGraw Hill 2006. [3] R.F. Pierret, “Semiconductor Device Fundamentals” Addison-Wesley Publishing Company, Inc. 1996. Characterization of a Geiger-Mode APD C. Maloney