Study of Surface Treatments on InAs/GaSb Superlattice LWIR Detectors

Abstract

We report on the comparison of mesa sidewall profiles of InAs/GaSb strainedlayer superlattice (SLS) detector structures (k 50% cutoff % 14 lm at V bias = 0 V and T = 30 K) obtained after (a) a conventional BCl 3 -based inductively coupled plasma etch, (b) a chemical etch (H 2 O 2 :HCl:H 2 O, 1:1:4), and (c) a combination of both etches. We found that the smoothest sidewall profile with reasonable undercut ($5 lm) was obtained after chemical etch only. The chemical etch was optimized primarily using an n-type GaSb substrate. During this process, numerous chemical etchants were examined. GaSb n-type substrates were chosen for this study in preference over InAs substrates due to their high chemical reactivity and the complicated composition of the native oxide. In addition, SLS detectors are usually grown on GaSb substrates and, after hybridization of the focal-plane array to the readout integrated circuit, the GaSb substrate is etched away using a combination of wet and dry etching techniques. We found that H 2 O 2 :HCl:H 2 O (1:1:4) etching solution provided the smoothest etched surface of GaSb, with a root-meansquare roughness of 1.59 nm.

Phonon Transport and Thermoelectricity in Defect-Engineered InAs Nanowires

“…The 1 µm wide windows patterned on the SiN x membrane of the shadow mask were aligned to the Pt electrodes. Following the shadow mask assembly, the NW was cleaned in O ଶ plasma for 10 seconds to remove any organic residue, and subsequently etched with BCl ଷ plasma for 20 seconds to remove the native oxide [13,14]. The device was then immediately mounted in the vacuum chamber of an electron beam evaporator for depositing 50 nm Ni and up to 150 nm Pd through the windows of the shadow mask onto the NW.…”

Passivation of long-wave infrared InAs/GaSb strained layer superlattice detectors

“…We attempted to partially restore the damage produced during the dry etch by subsequent HCl-based chemical treatment optimized earlier for InAs/GaSb SLS LWIR (k 50%-cut-off $ 14 lm at 30 K) material [16] In this work, we studied dielectric deposition (silicon nitride and silicon oxide), photoresist (SU-8), chalcogenide (ammonium sulfide and zinc sulfide), and electrochemical sulfur deposition for the reduction of surface leakage currents in type-II InAs/GaSb SLS detectors operating in the LWIR spectral region (100%-cut-off wavelength of $12 lm at 77 K). Detectors with conventional p-i-n and PbIbN [17] designs were fabricated with plasma-assisted (ICP) etch only.…”

InAs/GaSb Type-II Superlattice Detectors

“…Damage produced during the dry etch may be partially restored by subsequent chemical treatment [134]. Due to the ability of wet etches to cause virtually no surface electronic damage, a chemical etch attracts attention of researchers for single-pixel T2SL device fabrication [135][136][137][138][139][140]. However, the isotropic nature of wet etch process resulting in concave sidewall profile and an unavoidable tendency to undercut etch masks making precise dimensional control more difficult stipulates limited application of wet etches for T2SL FPA fabrication.…”