Avalanche-free tunnel-junction photodetectors with very high gain and responsivity

We present a prototype photodetector in which the built-in "tunneling structure" serves as an internal gain mechanism for photon detection. Initial feasibility studies demonstrated that the new photon detector offers an optical responsivity as high as 3000 A/W peaked at λ=1.3 μm at less than 1 V bias applied. The measurements were carried out using a photospectrometer setup in a continuous mode at room-temperature. Very strong (> 1000) responsivity is also measured from visible to SWIR even with a simple optical coupling scheme that utilizes very thin absorber layers in the prototype devices. The dark current density is ~ 5×10 -10 A/μm 2 at the operating bias. Room-temperature NEP was calculated based on a shot noise measurement, yielding NEP of 4~ 5×10 -15 W/Hz 1/2 and D* of 2~3×10 12 cmHz 1/2 /W, peaked at a bias of 0.3 V at a fixed wavelength of λ=1.3 μm.