Recent progress in extended wavelength InGaAs photodetectors and comparison with SWIR HgCdTe photodetectors

Abstract

At present, InGaAs and HgCdTe are still the primary choices of materials for 1-3μm short wavelength infrared (SWIR) photodetectors (photodiodes). Besides lattice matched 1.7μm cutoff standard InGaAs photodetectors, demands for extended wavelength (EW) InGaAs photodetectors (1.9-2.6μm cutoff) continue to grow in a broad range of markets such as Internet-of-Things (IoT), gas sensing, food processing, etc. This paper reviews recent progress in EW InGaAs photodetectors at Teledyne Judson Technologies (TJT). For 1.7μm cutoff at room temperature, InGaAs detectors generally have higher performance (lower dark current and higher shunt resistance) than the conventional SWIR HgCdTe detectors as characterized by the famous Rule-07 formula. In contrast, up to just recent years, EW InGaAs detectors generally had performance below the corresponding SWIR HgCdTe per Rule-07 for the same cutoff wavelength and operating temperature. The performance gap between the two materials became larger as the cutoff wavelength increases. This performance difference is primarily due to the lattice mismatch or strain induced defects in EW InGaAs materials. However, the recent progress in both EW InGaAs material growth and detector fabrication has resulted in dramatic improvement of EW InGaAs detector performance. The performance gap between the two materials is becoming much smaller or negligible at some wavelengths, while at other wavelengths, EW InGaAs even exceeds SWIR HgCdTe per Rule-07. In this paper, we will present recent detector performance data taken from EW InGaAs, as well as SWIR HgCdTe photodetectors, manufactured at TJT through state-of-the-art technologies. These discrete frontside illuminated detectors have sizes ranging from <0.25mm up to 5mm dia. and operate at temperatures from thermoelectric cooled (TEC, -20°C to -85°C) to above room temperature. An in-depth analysis of dark current density at reverse biases, as well as shunt resistance-area product at zero bias (R0A), over a broad temperature range, is performed. The data is compared with Rule-07 over the wavelength and temperature ranges of interest. Other detector performance parameters, such as spectral responsivity (quantum efficiency) and capacitance, are also compared between the two materials.