In this paper, we studied wet chemical etching fabrication of the InAs/GaSb superlattice mesa photodiode for the mid-infrared region. The details of the wet chemical etchants used for the device process are presented. The etching solution is based on orthophosphoric acid (H 3 PO 4 ), citric acid (C 6 H 8 O 7 ) and H 2 O 2 , followed by chemical polishing with the sodium hypochlorite (NaClO) solution and protection with photoresist polymerized. The photodiode performance is evaluated by current-voltage measurements. The zero-bias resistance area product R 0 A above 4 × 10 5 cm 2 at 77 K is reported. The device did not show dark current degradation at 77 K after exposition during 3 weeks to the ambient air.

We report on structural, electrical, and optical characterizations of midwave infrared InAs/GaSb superlattice (SL) p-i-n photodiodes. High-quality SL samples, with 1 μm thick active region (220 SL periods), exhibited a cut-off wavelength of 4.9 μm at 80 K. Using a capacitance-voltage measurement technique performed on mesa diode, the residual background concentration in the nonintentionally doped region was determined to be 3×1015 cm−3 at 80 K. Extracted from current-voltage characteristics, R0A products above 4×105 Ω cm2 at 80 K were measured, and the quantitative analysis of the J-V curves showed that the dark current density of SL photodiode is dominated by generation-recombination processes. Front-side illuminated photodiodes produced responsivity at 80 K equal to 360 mA/W at 4.5 μm.

In this communication we report on electrical properties of nonintentionally doped (nid) type II InAs/GaSb superlattice grown by molecular beam epitaxy. We present a simple technological process which, thanks to the suppression of substrate, allows direct Hall measurement on superlattice structures grown on conductive GaSb substrate. Two samples were used to characterize the transport: one grown on a semi-insulating GaAs substrate and another grown on n-GaSb substrate where a etch stop layer was inserted to remove the conductive substrate. Mobilities and carrier concentrations have been measured as a function of temperature (77–300 K), and compared with capacitance-voltage characteristic at 80 K of a photodiode comprising a similar nid superlattice.

We present a type-II superlattice period with a modified InAs to GaSb thickness ratio for midinfrared detection. In this kind of structure, the large electron-hole wave-function overlap and the low intrinsic carrier concentration lead to a significant signal-to-noise ratio enhancement. For the proof of concept, a sample designed with an InAs to GaSb thickness ratio close to 2 was grown. Comparison with standard design photodiodes shows an improvement of the differential resistance area product by one and a half decade while the quantum efficiency was more than doubled.

No abstract

No abstract

No abstract

This paper presents recent developments done at CEA-LETI Infrared Laboratory on processing and characterization of p-on-n HgCdTe (MCT) planar infrared focal plane arrays (FPAs) in LWIR and VLWIR spectral bands. These FPAs have been grown using liquid phase epitaxy (LPE) on a lattice matched CdZnTe substrate. This technology presents lower dark current and lower serial resistance in comparison with n-on-p vacancy doped architecture and is well adapted for low flux detection or high operating temperature. This architecture has been evaluated for space applications in LWIR and VLWIR spectral bands with cutoff wavelengths from 10µm up to 17µm at 78K. Innovations have been introduced to the technological process to form a heterojunction with a LPE growth technique. The aim was to lower dark current at low temperature, by decreasing currents from the depletion region. Electro-optical characterizations on p-on-n photodiodes have been performed on QVGA format FPAs with 30µm pixel pitches. Results show excellent operabilities in current and responsivity, with low dispersion and noise limited by current shotnoise. Studies performed on dark current show that dark current densities are consistent with the heuristic prediction law "Rule07" at 78K. Below this temperature, dark current varies as a pure diffusion current.