Extended wavelength SWIR InGaAs focal plane array: Characteristics and limitations

• Extended wavelength InGaAs detectors MBE grown on InP substrate are demonstrated.
• Dark current mechanisms in extended InGaAs detectors are studied.
• InGaAs detector performance is determined by G–R and ohmic leakage mechanisms.
• No tunneling component is observed at typical operating conditions.
• We report extended InGaAs focal plane array with 2.6 μm cut-off.

We present the characteristics of large format (640 × 512) short wavelength infrared (SWIR) InGaAs photodetector focal plane array (FPA) with ∼2.65 μm room temperature cut-off wavelength. The detector epilayers were grown with solid source molecular beam epitaxy on InP substrates using a linearly graded InAlAs buffer layer. In spite of the large lattice mismatch, the FPA yields reasonably good responsivity nonuniformity (9%) with a pixel detectivity above 2 × 1010 cm Hz1/2/W at room temperature. The dark current of the pixels are dominated by generation–recombination (G–R) and shunt leakage mechanisms with negligible tunneling above 200 K up to a reverse bias voltage of 3 V. The results are very encouraging for further study toward the optimization of the epilayer structure and growth conditions in order to provide a lower cost technology alternative to HgCdTe in the SWIR band.