Electric Gain Effect in LWIR ICIPs Under Thermoelectric Cooling (200/230 K)

Abstract

This article presents an analysis of the electric gain in interband cascade infrared photodetectors (ICIPs) impacting the final performance of the long-wavelength infrared (LWIR) detectors fabricated in VIGO Photonics S.A. (VIGO) and optimized for 200 and 230 K. The aim is to illustrate the presence of the gain in selected ICIP structures, as well as to demonstrate its dependence on the carrier diffusion length and series resistance versus operating temperatures. All analyzed devices are based on the InAs/InAsSb type-II superlattice (T2SLs) with subsequent cells connected by highly doped p+/n+ tunnel junctions. Additionally, to increase the optical area and signal-to-noise ratio, immersion lenses were processed in all devices. This article focuses on the electric gain analysis, being defined as the ratio of the measured current responsivity and the theoretically simulated one based on the active layer absorption coefficient. Furthermore, this article presents the impact of a double radiation pass through the last stage of the cascade structure after its reflection from the metallization on quantum efficiency (QE), current responsivity, and gain from the simulations.