Linearity Characterisation of High-Performance SWIR Photodetectors
Henry Yuan, Kai Song, Andrey Rumyantsev, David Bond, Lori Harris, Joe Kimchi, Jih-Fen Lei
Teledyne Judson Technologies
Background
Teledyne Judson Technologies (TJT) has been advancing extended wavelength (EW) InGaAs photodetector technology with cut-off wavelengths from 1.9 µm to 2.6 µm. InGaAs remains one of the most important materials for short-wave infrared (SWIR) detection thanks to its low dark current, mature fabrication processes, and ability to operate near room temperature. Demand for extended wavelength capability continues to grow in applications such as thermal and gas sensing, spectroscopy, food safety, and IoT systems.
Historically, EW InGaAs detectors exhibited significantly higher dark current and lower resistance-area product (Râ‚€A) than MCT devices at equivalent cut-off wavelengths and operating temperatures. The performance gap was particularly wide at longer wavelengths and lower temperatures, limiting the adoption of EW InGaAs in certain SWIR applications.
Challenge
The primary limitation of EW InGaAs performance compared to MCT has been the increased defect density caused by lattice mismatch between the InGaAs absorber and the InP substrate. As the cut-off wavelength increases, higher indium content leads to greater lattice strain and defect formation, resulting in higher dark current and lower Râ‚€A.
At lower temperatures, additional defect-related mechanisms such as generation-recombination and trap-assisted tunnelling become dominant, further reducing device performance. Surface and interface states can also contribute to leakage currents, particularly in devices with smaller active areas. Historically, these issues meant that EW InGaAs devices fell several times below the theoretical performance limit predicted by the widely used Rule 07 model for state-of-the-art MCT photodiodes.
Figure 1: Test setup block diagram of photoresponse linearity measurement.
Solution
TJT has addressed these limitations through significant improvements in materials growth, device design, and processing. Advances in metal-organic chemical vapour deposition (MOCVD) growth, including improved lattice accommodation layers, have reduced defect densities and extended carrier lifetimes. Refinements in epitaxial structure and passivation techniques have lowered surface and perimeter leakage currents.
Device design improvements have also included optimised diode geometries and the use of gate-controlled structures to better manage surface potential and suppress interface-related leakage. These steps collectively improve both the diffusion and generation-recombination current limits, shifting the dominant dark current mechanisms closer to those seen in ideal p–n junction photodiodes.
Results
These advances have led to a dramatic improvement in EW InGaAs detector performance. Across all cut-off wavelengths and device sizes, Râ‚€A has increased by factors of three to ten compared to previous catalog specifications, and in some cases by up to two orders of magnitude. At room temperature, for example, typical Râ‚€A values for 2.6 µm detectors increased from a few ohm-cm² to tens of ohm-cm², while at lower temperatures improvements were even more pronounced.
At -40 °C and below, the best-performing detectors now approach or exceed the Rule 07 model for MCT, demonstrating that diffusion and generation-recombination current suppression has been highly effective. Carrier lifetime improvements are significant, with minority carrier lifetimes increasing by more than two orders of magnitude and Shockley-Read-Hall recombination lifetimes showing similar enhancements.
Importantly, these improvements are not limited to small test structures. Full production detectors across 1-3 mm diameters now show excellent uniformity and high yield, with most devices meeting or exceeding theoretical performance expectations across a wide range of temperatures. In some cases, EW InGaAs devices slightly outperform equivalent MCT detectors.
Conclusion
The recent progress achieved at TJT marks a turning point for extended wavelength InGaAs photodetectors. Through targeted improvements in materials, device design, and processing, EW InGaAs performance has advanced to the point where it matches or surpasses MCT in many SWIR applications.
This breakthrough closes a long-standing performance gap and positions EW InGaAs as a highly competitive technology for applications requiring low dark current, high resistance, and extended wavelength sensitivity. All while maintaining the cost, reliability, and integration advantages inherent to InGaAs-based solutions.
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Linearity characterization of high performance SWIR photodetectors from various materials
Henry Yuan, Kai Song, Andrey Rumyantsev, David Bond, Lori Harris, Joe Kimchi, Jih-Fen Lei
Abstract
comprehensive study of photoresponse linearity characteristics, for high performance short wavelength infrared (SWIR) photodiodes of various materials, is performed. These photovoltaic (PV) detectors were manufactured at Teledyne Judson Technologies (TJT) as standard products, with the state-of-the-art technologies. A broad range of detectors made from several IR materials were selected for linearity tests, including InGaAs (cutoff wavelength from lattice matched 1.7μm to extended wavelength of 1.9-2.6μm), SWIR PV HgCdTe (2.5-2.8μm cutoff), Ge (1.8μm cutoff), and InAs (3.5μm cutoff). Comprehensive linearity test data are presented for each detector material. Characterization of linearity dependence on detector size, operating temperature, reverse bias, and light spot size is studied. Detector size ranges from <0.25mm dia. up to 10mm dia., detector operating temperature from room temperature to thermoelectric cooled (TEC) temperatures, detector bias from 0V up to 10V reverse bias for some materials, and light spot size from 10μm up to 1mm. This work focuses on photocurrent saturation in the high optical power (or photon flux) range. Two saturation mechanisms are investigated, including series resistance effect and Auger recombination effect.
Reference
Henry Yuan, Kai Song, Andrey Rumyantsev, David Bond, Lori Harris, Joe Kimchi, and Jih-Fen Lei (1 March 2019) Linearity characterization of high performance SWIR photodetectors from various materials, Proc. SPIE 10914, Optical Components and Materials XVI, 1091415; https://doi.org/10.1117/12.2511904
