Advances on Sensitive Electron-Injection Based Cameras for Low-Flux, Short-Wave Infrared Applications

Abstract

Short-wave infrared (SWIR) photon detection has become an essential technology in the modern world. Sensitive SWIR detector arrays with high pixel density, low noise levels, and high signal-to-noise-ratios are highly desirable for a variety of applications including biophotonics, light detection and ranging, optical tomography, and astronomical imaging. As such many efforts in infrared detector research are directed toward improving the performance of the photon detectors operating in this wavelength range. We review the history, principle of operation, present status, and possible future developments of a sensitive SWIR detector technology, which has demonstrated to be one of the most promising paths to high pixel density focal plane arrays (FPAs) for low flux applications. The so-called electron-injection (EI) detector was demonstrated for the first time in 2007. It offers an overall system-level sensitivity enhancement compared to the p-i-n diode due to a stable internal avalanche-free gain. The amplification method is inherently low noise, and devices exhibit an excess noise of unity. The detector operates in linear-mode and requires only bias voltage of a few volts. This together with the feedback stabilized gain mechanism, makes formation of large-format high pixel density electr on-injection FPAs less challenging compared to other detector technologies such as avalanche photodetectors. Detector is based on the mature InP material system and has a cutoff wavelength of 1700 nm. The layer structure consists of 500 nm InP injector/50 nm InAlAs etch stop/50 nm GaAsSb electron barrier (and hole trap)/1 μm InGaAs absorber. The epitaxial layers are grown on InP substrates. Electron-injection detector takes advantage of a unique three-dimensional geometry and combines the efficiency of a large absorbing volume with the sensitivity of a low-dimensional switch (injector) to sense and amplify signals. EI detectors have been designed, fabricated, and tested during two generations of development and optimization cycles. We review our imager results using the firstgeneration detectors. In the second-generation devices, the dark current is reduced by two orders of magnitude, and bandwidth is improved by four orders of magnitude. The dark current density of the second-generation EI detector is shown to outperform the stateof-the-art technology, the SWIR HgCdTe eAPD by more than one order of magnitude. We demonstrate a performance comparison with other SWIR detector technologies with internal amplification and show that the electron-injection detectors offer more than three orders of magnitude better noise-equivalent sensitivity compared with state-of-the-art phototransistors operating at similar temperature. Second-generation devices provide high-speed response ~6 ns rise time, low jitter ~12 ps, high amplification of more than FiGURe 1 | The trend in noise reduction for state-of-the-art SwiR imaging arrays with cutoff wavelength (λc) ~1-1.5 μm over the past 30 years: the equivalent input noise of the ROiC determines the ...

Single-Photon Counting with Semiconductor Resonant Tunneling Devices

“…High quantum efficiencies and an enhanced gating of the majority charge carrier current can be reached simultaneously. The detection of weak light pulses down to a few photons has been demonstrated, and the nano-injector is considered particularly apt for imaging applications and focal plane arrays [ 51 ]. The nano-injector design has only been used for devices in the InP/InGaAs material system, even though there are no apparent restraints from its application in other semiconductor material systems.…”

Design and Implementation Guidelines for a Modular Spectral-Domain Optical Coherence Tomography Scanner

“…Although such detectors are sufficiently fast for many applications, faster and more sensitive detectors are beneficial in certain in vivo experiments, for example, to reduce motion artifacts or perform Doppler velocimetry of fast moving particles. By employing the new state-of-the-art electron-injection based detectors [76], it is possible to improve the sensitivity and dynamic range of the OCT imaging systems at higher imaging speeds.…”

Substrate-Independent Broad-Band Immersion Microlens Arrays with a High Coupling Efficiency for Infrared Focal Plane Arrays

“…4−6 Nonetheless, the sensitivity of IR imagers has not matched these demands despite intense research in this field. 7,8 Most efforts toward increasing sensitivity revolve around the development of smaller photodetectors. 9−15 This follows from the definition of specific detectivity, a common metric of sensitivity, 16 as given by eq 1…”

“…They have found applications in a wide range of fields, including astronomy, biomedicine, military, and manufacturing. − As the range of applications grows, the demand is for IR cameras with increasingly high sensitivities. As an example, the field of exoplanet detection does not yet have an IR camera with the high-speed sensitivity needed to image Earth-like exoplanets in the habitable zone of distant stars. − Nonetheless, the sensitivity of IR imagers has not matched these demands despite intense research in this field. , …”