International audienc

We present a full characterization of the radiometric performances of a type-II InAs/GaSb superlattice pin photodiode operating in the mid-wavelength infrared domain. We first focused our attention on quantum efficiency, responsivity and angular response measurements: quantum efficiency reaches 23% at λ = 2.1 µm for 1 µm thick structure. Noise under illumination measurements are also reported: noise is limited by the Schottky contribution for reverse bias voltage smaller than 1.2 V. The specific detectivity, estimated for 2π field-of-view and 333 K background temperature, was determined equal to 2.29 × 1010 Jones for -0,8 V bias voltage and 77 K operating temperature.

GaSb-rich superlattice (SL) p-i-n photodiodes grown by molecular beam epitaxy were studied theoretically and experimentally in order to understand the poor dark current characteristics typically obtained. This behavior, independent of the SL-grown material quality, is usually attributed to the presence of defects due to Ga-related bonds, limiting the SL carrier lifetime. By analyzing the photoresponse spectra of reverse-biased photodiodes at 80 K, we have highlighted the presence of an electric field, breaking the minibands into localized Wannier-Stark states. Besides the influence of defects in such GaSb-rich SL structures, this electric field induces a strong tunneling current at low bias which can be the main limiting mechanism explaining the high dark current density of the GaSb-rich SL diode.

Midwave infrared (MWIR) InAs/GaSb superlattice (SL) photodiode with a dopant-free p-n junction was fabricated by molecular beam epitaxy on GaSb substrate. Depending on the thickness ratio between InAs and GaSb layers in the SL period, the residual background carriers of this adjustable material can be either n-type or p-type. Using this flexibility in residual doping of the SL material, the p-n junction of the device is made with different nonintentionally doped (nid) SL structures. The SL photodiode processed shows a cutoff wavelength at 4.65µm at 77K, residual carrier concentration equal to 1.75x10 15 cm-3 , dark current density as low as 2.8x10-8 A/cm 2 at 50 mV reverse bias and R0A product as high as 2x10 6 .cm 2. The results obtained demonstrate the possibility to fabricate a SL pin photodiode without intentional doping the pn junction. Highlights :-MWIR SL photodiode was made using the flexibility properties of InAs/GaSb Superlattice-MWIR SL photodiode was made without intentional doping the pn junction-Electrical and electro-optical characterizations of MWIR pin SL photodiode made of dopant-free p-n junction have been reported