Xudong Jiang

Advances in InGaAsP-based avalanche diode single photon detectors

In this Topical Review, we survey the state-of-the-art of single photon detectors based on avalanche diodes fabricated in the InGaAsP materials system for photon counting at near infrared wavelengths in the range from 0.9–1.6 µm. The fundamental trade-off between photon detection efficiency and dark count rate can now be managed with performance that adequately serves many applications, with low dark count rates of ∼1 kHz having been demonstrated at photon detection efficiencies of 20% for 25 µm diameter fiber-coupled devices with thermoelectric cooling. Timing jitter of less than 50 ps has been achieved, although device uniformity is shown to be essential in obtaining good jitter performance. Progress is also reported towards resolving the limitations imposed on photon counting rate by afterpulsing, with at least 50 MHz repetition frequencies demonstrated for 1 ns gated operation with afterpulsing limited to the range of 1–5%. We also present a discussion of future trends and challenges related to these devices organized according to the hierarchy of materials properties, device design concepts, signal processing and electronic circuitry, and multiplexing concepts. Whereas the materials properties of these devices may pose significant challenges for the foreseeable future, there has been considerable progress in device concepts and circuit solutions towards the present imperatives for higher counting rates and simpler device operation.

InGaAsP–InP Avalanche Photodiodes for Single Photon Detection

In this paper, we describe the design, characterization, and modeling of InGaAsP/InP avalanche diodes designed for single photon detection at wavelengths of 1.55 and 1.06 mum. Through experimental and theoretical work, we investigate critical performance parameters of these single photon avalanche diodes (SPADs), including dark count rate (DCR), photon detection efficiency (PDE), and afterpulsing. The models developed for the simulation of device performance provide good agreement with experimental results for all parameters studied. For 1.55-mum SPADs, we report the relationship between DCR and PDE for gated mode operation under a variety of operating conditions. We also describe in detail the dependence of afterpulsing effects on numerous operating conditions, and in particular, we demonstrate and explain a universal functional form that describes the dependence of DCR on hold-off time at any temperature. For 1.06-mum SPADs, we present the experimentally determined relationship between DCR and detection efficiency for free-running operation, as well as simulations complementing the experimental data.

Power law temporal dependence of InGaAs/InP SPAD afterpulsing

The characterization and analysis of afterpulsing behavior in InGaAs/InP single photon avalanche diodes (SPADs) is reported for gating frequencies between 10 and 50 MHz. Gating in this frequency range was accomplished using a matched delay line technique to achieve parasitic transient cancellation, and FPGA-based data acquisition firmware was implemented to provide an efficient, flexible multiple-gate sequencing methodology for obtaining the dependence of afterpulse probability P ap on hold-off time T ho. We show that the detrapping times extracted from the canonical exponential fitting of P ap(T ho) have no physical significance, and we propose an alternative description of the measured data, which is accurately fit with the simple power law behavior P ap ∝  with α ∼ 1.2 ± 0.2. We discuss the physical implications of this functional form, including what it may indicate about trap defect distributions and other possible origins of this power law behavior.

Geiger-mode avalanche photodiode focal plane arrays for three-dimensional imaging LADAR

We report on the development of focal plane arrays (FPAs) employing two-dimensional arrays of InGaAsP-based Geiger-mode avalanche photodiodes (GmAPDs). These FPAs incorporate InP/InGaAs(P) Geiger-mode avalanche photodiodes (GmAPDs) to create pixels that detect single photons at shortwave infrared wavelengths with high efficiency and low dark count rates. GmAPD arrays are hybridized to CMOS read-out integrated circuits (ROICs) that enable independent laser radar (LADAR) time-of-flight measurements for each pixel, providing three-dimensional image data at frame rates approaching 200 kHz. Microlens arrays are used to maintain high fill factor of greater than 70%. We present full-array performance maps for two different types of sensors optimized for operation at 1.06 μm and 1.55 μm, respectively. For the 1.06 μm FPAs, overall photon detection efficiency of >40% is achieved at <20 kHz dark count rates with modest cooling to ~250 K using integrated thermoelectric coolers. We also describe the first evalution of these FPAs when multi-photon pulses are incident on single pixels. The effective detection efficiency for multi-photon pulses shows excellent agreement with predictions based on Poisson statistics. We also characterize the crosstalk as a function of pulse mean photon number. Relative to the intrinsic crosstalk contribution from hot carrier luminescence that occurs during avalanche current flows resulting from single incident photons, we find a modest rise in crosstalk for multi-photon incident pulses that can be accurately explained by direct optical scattering.

Free-running single-photon detection based on a negative feedback InGaAs APD

InGaAs/InP-based semiconductor avalanche photodiodes are usually employed for single-photon counting at telecom wavelength. However they are affected by afterpulsing which limits the diode performance. Recently, Princeton Lightwave has commercialized a diode integrating monolithically a feedback resistor. This solution effectively quenches the avalanche and drastically reduces afterpulsing. Here, we report the development and characterization of a detector module based on this diode, implementing an active hold-off circuit which further reduces the afterpulsing and notably improves the detector performances. We demonstrate free-running operation with 600 Hz dark count rate at 10% detection efficiency. We also improved the standard double-window technique for the afterpulsing characterization. Our algorithm implemented by a FPGA allows one to put the APD in a well-defined initial condition and to measure the impact of the higher order afterpulses.

InP-based Geiger-mode avalanche photodiode arrays for three-dimensional imaging at 1.06 μm

We report on the development of 32 x 32 focal plane arrays (FPAs) based on InGaAsP/InP Geiger-mode avalanche photodiodes (GmAPDs) designed for use in three-dimensional (3-D) laser radar imaging systems at 1064 nm. To our knowledge, this is the first realization of FPAs for 3-D imaging that employ a planar-passivated buried-junction InP-based GmAPD device platform. This development also included the design and fabrication of custom readout integrate circuits (ROICs) to perform avalanche detection and time-of-flight measurements on a per-pixel basis. We demonstrate photodiode arrays (PDAs) with a very narrow breakdown voltage distribution width of 0.34 V, corresponding to a breakdown voltage total variation of less than +/- 0.2%. At an excess bias voltage of 3.3 V, which provides 40% pixel-level single photon detection efficiency, we achieve average dark count rates of 2 kHz at an operating temperature of 248 K. We present the characterization of optical crosstalk induced by hot carrier luminescence during avalanche events, where we show that the worst-case crosstalk probability per pixel, which occurs for nearest neighbors, has a value of less than 1.6% and exhibits anisotropy due to isolation trench etch geometry. To demonstrate the FPA response to optical density variations, we show a simple image of a broadened optical beam.

Afterpulsing Effects in Free-Running InGaAsP Single-Photon Avalanche Diodes

We demonstrate large-area (80 mum diameter) InP-based single-photon avalanche diodes for Geiger-mode operation at 1.06 mum with dark count rates of ~1000 Hz at high detection efficiencies of 30% at 237 K, as well as simulations of dark count rate and detection efficiency that provide good agreement with measured data. Experimental results obtained using free-running operation illustrate the strong impact of afterpulsing effects for short (~200 ns) hold-off times. We present an analysis of these free-running results that quantifies the contribution of afterpulsing to the total count rate.

Geiger-mode APD camera system for single-photon 3D LADAR imaging

The unparalleled sensitivity of 3D LADAR imaging sensors based on single photon detection provides substantial benefits for imaging at long stand-off distances and minimizing laser pulse energy requirements. To obtain 3D LADAR images with single photon sensitivity, we have demonstrated focal plane arrays (FPAs) based on InGaAsP Geiger-mode avalanche photodiodes (GmAPDs) optimized for use at either 1.06 μm or 1.55 μm. These state-of-the-art FPAs exhibit excellent pixel-level performance and the capability for 100% pixel yield on a 32 x 32 format. To realize the full potential of these FPAs, we have recently developed an integrated camera system providing turnkey operation based on FPGA control. This system implementation enables the extremely high frame-rate capability of the GmAPD FPA, and frame rates in excess of 250 kHz (for 0.4 μs range gates) can be accommodated using an industry-standard CameraLink interface in full configuration. Real-time data streaming for continuous acquisition of 2 μs range gate point cloud data with 13-bit time-stamp resolution at 186 kHz frame rates has been established using multiple solid-state storage drives. Range gate durations spanning 4 ns to 10 μs provide broad operational flexibility. The camera also provides real-time signal processing in the form of multi-frame gray-scale contrast images and single-frame time-stamp histograms, and automated bias control has been implemented to maintain a constant photon detection efficiency in the presence of ambient temperature changes. A comprehensive graphical user interface has been developed to provide complete camera control using a simple serial command set, and this command set supports highly flexible end-user customization.

Common-Mode Cancellation in Sinusoidal Gating With Balanced InGaAs/InP Single Photon Avalanche Diodes

We demonstrate a sinusoidal-gated InGaAs/InP single photon avalanche diode (SPAD) pair with high photon detection efficiency (PDE) and low dark count rate (DCR). The photodiode pair is biased in a balanced configuration with only one of the SPADs illuminated. The advantage of balanced detectors is cancellation of the common component of the output signal, which in this case arises from sinusoidal gating. In conventional sinusoidal gating, narrow-band RF filters are used to eliminate the gating signal while imparting minimal change to the avalanche pulses. A disadvantage of this approach is that the requisite filters fix the operating frequency, whereas the balanced SPAD receiver is frequency agile. At a laser repletion rate of 1 MHz and a temperature of 240 K, the DCR and PDE are 58 kHz and 43%, respectively. The afterpulse probability is lower than a single sinusoidal-gated SPAD. Jitter of 240 ps is achieved with one photon per pulse and an excess bias of 1.6%.

Characterization of an InGaAs/InP-based single-photon avalanche diode with gated-passive quenching with active reset circuit

An improved gated-mode passive quenching with active reset (gated-PQAR) circuit is utilized in conjunction with an InGaAs/InP single-photon avalanche photodiode (SPAD). Photon detection efficiency (PDE) and dark count probability (DCP) were measured at a gate repetition rate of 1 MHz. The reduced afterpulsing afforded by the gated-PQAR circuit enabled measurement of afterpulsing for hold-off times as short as 10 ns. The timing resolution (jitter) for different excess biases has also been investigated. At 230 K and an excess bias of 2.5 V, 0.3% afterpulse probability for a 10 ns hold-off time was achieved with 13% PDE, 2 × 10−6 DCP, 160 ps jitter, and 0.2 ns effective gate width. For the same hold-off time, at a higher excess bias of 3.5 V, 30% PDE, 1 × 10−5 DCP and 120 ps jitter were achieved with 7% afterpulse probability with an effective gate width of 0.7 ns.