Low Dark Current Operation in InAs/GaAs(111)A Infrared Photodetectors: Role of Misfit Dislocations at the Interface

Wedemonstrate an extended short-wave infrared (e-SWIR)photodetector composed of an InAs/GaAs(111)A heterostructurewith interface misfit dislocations. The layer structure of the photodetectorconsists simply of an n-InAs optical absorption layerdirectly grown with a thin undoped-GaAs spacer layer on n-GaAs by molecular beam epitaxy. The lattice mismatch was abruptlyrelaxed by forming a misfit dislocation network at the initial stageof the InAs growth. We found high-density threading dislocations (1.5x 10(9) cm(-2)) in the InAs layer. Thecurrent-voltage characteristics of the photodetector at 77K had a very low dark current density (<1 x 10(-9) A cm(-2)) at a positive applied voltage (electronsflow from n-GaAs to n-InAs) of upto similar to+1 V. Simulation of the band structure revealed that thedirect connection of GaAs and InAs and the formation of interfacialstates by the misfit dislocations play significant positive rolesin suppressing dark current. Under illumination with e-SWIR light at 77 K, a clear photocurrent signal was observed witha 2.6 mu m cutoff wavelength, which is consistent with the bandgapof InAs. We also demonstrated e-SWIR detection atroom temperature with a 3.2 mu m cutoff wavelength. The maximumdetectivity at 294 K exceeds 2 x 10(8) cm Hz(0.5) W-1 for the detection of e-SWIRlight at 2 mu m.

Automated summary

We demonstrate an extended short-wave infrared (e-SWIR) photodetector with interface misfit dislocations in an InAs/GaAs(111)A heterostructure. The photodetector consists of an n-InAs absorption layer directly grown on n-GaAs with a thin undoped-GaAs spacer layer. The formation of a misfit dislocation network in the InAs growth stage helps relax the lattice mismatch and suppress dark current, leading to efficient e-SWIR detection.