Xue Li

In this work, a high-performance mid-wave infrared (MWIR) photodetector (PD) utilizing an InAs/GaSb Type-II superlattice absorber and a quaternary AlGaAsSb barrier is designed and analyzed based on numerical simulations aimed at determining an optimized detector structure. Through these simulations, the composition of the AlGaAsSb barrier is carefully designed to achieve lattice matching, high conduction band offset and zero valence band offset. By optimizing the barrier thickness and doping concentration, the depletion region is effectively shifted from the narrow-bandgap absorber to the wide-bandgap barrier; additionally, at 150 K and a reversed bias of 0.05 V, the dark current density in the PD with the barrier (pBn) is reduced to 1.83 × 10⁻⁵ A/cm², about two orders of magnitude lower than that of the PD without the barrier. Furthermore, the effect of the barrier on the generation–recombination (G-R) and the trap-assisted tunneling (TAT) currents are analyzed and compared in detail, and it is found that the barrier structure is much more effective in suppressing the TAT current at low reversed bias when the electric field is low in the absorber layer. These results demonstrate the efficacy of the proposed AlGaAsSb barrier design for realizing high-operating-temperature MWIR PDs. It also provides an insight into the physical mechanism that leads to the performance enhancement of InAs/GaSb PDs.

Zinc diffusion behaviors in n type In0.83Ga0.17As epitaxial layers doped to 3.5 × 1015 cm−3 are investigated for the planar type extended wavelength In0.83Al0.17As/In0.83Ga0.17As focal plane arrays by incorporating the vacancy-related complex defect (VCD) model. The diffusion coefficients extracted from the measured zinc concentration profiles at 480 °C are determined to be 3.1 × 10−12 and 4.3 × 10−11 cm2/s for the kick-out and the VCD models, respectively. Both mechanisms compete with each other during the dynamic zinc atom drive-in process. The diffusion activation energies for two mechanisms are 0.56 and 0.06 eV, indicating that the VCD model is not quite sensitive to the temperature compared with the kick-out model. The higher diffusion coefficient of the VCD model renders the occurrence of an anomalous rapid drive-in process with a lower concentration in the lightly doped epitaxial layer, leading to the increased dark current densities of 0.052 A/cm2 at 300 K and 8.85 × 10−7 A/cm2 at 140 K with −10 mV bias. By precise control of the diffusion depth, low dark current densities at −10 mV were obtained with 1.84 × 10−3 A/cm2 at 300 K and 4.5 × 10−9 A/cm2 at 140 K. The high peak specific detectivity (D*) up to 1.89 × 1013 cm Hz1/2 W−1 is achieved under a long integration time of 400 ms with the pixel operability of 99.4%.

A planar In0.53Ga0.47As avalanche photodiode (APD) with a triple-stage cascaded InAlAs/InAlGaAs multiplication structure is designed and fabricated. Double zinc-diffusion p-n junction is formed to suppress the perimeter premature breakdown. A low dark current of 4.8 nA at around breakdown voltage is obtained at room temperature for a $40~\mu $ m diameter device with a maximum gain-bandwidth product of 216 GHz. The E-field profile is modulated by doping of a thin In0.52Al0.48As subcharge layer within each multiplication stage. Moreover, electron and hole potential wells are also introduced by the In0.52Al0.24Ga0.24As layers within each stage. The measured hole-initiated maximum gain factor and excess noise factor are 77 and F=6.3 at 200 K, respectively, which well agree with the predicted results base on the dead-space multiplication theory. These results indicate the planar multi-stage multiplication regime is a viable route for fabrication of APDs towards low excess noise while maintaining of a low dark current.

Shortwave infrared polarization imaging can increase the contrast of the target to the background to improve the detection system’s recognition ability. The division of focal plane polarization indium gallium arsenide (InGaAs) focal plane array (FPA) detector is the ideal choice due to the advantages of compact structure, real-time imaging, and high stability. However, because of the mismatch between nanostructures and photosensitive pixels as well as the crosstalk among the different polarization directions, the currently reported extinction ratio (ER) of superpixel-polarization-integrated detectors cannot meet the needs of high-quality imaging. In this paper, a 1024 × 4 InGaAs FPA detector on-chip integrated with a linear polarization grating (LPG) was realized and tested. The detector displayed good performance throughout the 0.9–1.7 um band, and the ERs at 1064 nm, 1310 nm and 1550 nm reached up to 22:1, 29:1 and 46:1, respectively. For the crosstalk investigation, the optical simulation of the grating-integrated InGaAs pixel was carried out, and the limitation of the ER was calculated. The result showed that the scattering of incident light in the InP substrate led to the crosstalk. Moreover, the deviation of the actual grating morphology from the designed structure caused a further reduction in the ER.

Dark current behaviors of the 2.6 μm cutoff wavelength In _0.83 Ga _0.17 As photodetectors are investigated as a function of the mesa etching depth. The total dark current monotonically declines from 2.0×10 ^-6 A/cm ² to 8.3×10 ^-7 A/cm ² at 180 K and -10 mV as the mesa etching depth decreases from 2.6 to 0.9 μm. Meanwhile, an order of magnitude lower surface leakage current from 4.56 to 0.47 nA/cm, and a narrower statistical distribution are observed simultaneously. Moreover, the 300 K peak detectivity and quantum efficiency increase from 2.6×10 ¹¹ to 5.4×10 ¹¹ cmHz ^1/2 /W and from 67.1% to 71.2%, respectively, as the mesa etching depth decreases from 2.6 to 0.9 μm, benefit from the lateral carrier collection effect. These results suggest shallow mesa structures are indispensable towards surface leakage free In _0.83 Ga _0.17 As photodetectors.

A visible–extended shortwave infrared indium gallium arsenide (InGaAs) focal plane array (FPA) detector is the ideal choice for reducing the size, weight and power (SWaP) of infrared imaging systems, especially in low-light night vision and other fields that require simultaneous visible and near-infrared light detection. However, the lower quantum efficiency in the visible band has limited the extensive application of the visible–extended InGaAs FPA. Recently, a novel optical metasurface has been considered a solution for a high-performance semiconductor photoelectric device due to its highly controllable property of electromagnetic wave manipulation. Broadband Mie resonator arrays, such as nanocones and nanopillars designed with FDTD methods, were integrated on a back-illuminated InGaAs FPA as an AR metasurface. The visible–extended InGaAs detector was fabricated using substrate removal technology. The nanostructures integrated into the Vis-SWIR InGaAs detectors could realize a 10–20% enhanced quantum efficiency and an 18.8% higher FPA response throughout the wavelength range of 500–1700 nm. Compared with the traditional AR coating, nanostructure integration has advantages, such as broadband high responsivity and omnidirection antireflection, as a promising route for future Vis-SWIR InGaAs detectors with higher image quality.

In the above article [1] , the affiliations were written as:

The dark current and the photo response characteristics of extended wavelength In _0.83 Ga _0.17 As/InP photodetectors (PDs) with n-In _0.83 Ga _0.17 As absorber doped to 8×10 ¹⁵ , 7×10 ¹⁶ and 1×10 ¹⁷ cm ^-3 are investigated in an elevated temperature range of -40 to 100°C. The lightly doped PD exhibits a lower (higher) dark current than the heavily doped PD at temperatures higher (lower) than 30°C. The photocurrent, the spectral responsivity and the blackbody response voltage for the heavily doped PD rapidly decrease at temperatures higher than 30°C, while remain almost unchanged until 90°C for the lightly doped PD. The trend of the intermediately doped PD is between the two. In contrast, a consistently increasing trend of the dark noise over the whole measured temperature range are observed for three PDs. Theoretical calculations indicate such behaviors are essentially related with the temperature-dependent variation of the Shockley-Read-Hall lifetimes under different doping concentration.