Wet etching and chemical polishing of InAs/GaSb superlattice photodiodes

Abstract

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.

Edge transport in InAs and InAs/GaSb quantum wells

“…Others also add the effect of electric field line concentration, present when gates overlap the sample edges. Edge conduction may also be a side effect of sample processing, either after long exposure to air [25] or because of conducting Sb residues on the surface after etching [26]. Our experiments add to these results that edge conduction can occur in pure InAs quantum well samples and that it may dominate transport if the bulk is insulating.…”

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

“…Photodetectors operating in the long-wave infrared (LWIR, [8][9][10][11][12][13][14] lm) spectral band could be potentially useful for a wide variety of applications such as meteorology, astrophysical imaging, missile detection and tracking, and satellite based surveillance. The technologies currently dominating those applications in this wavelength range are based on interband Mercury-CadmiumTelluride (MCT) and intersubband quantum well infrared (QWIP) detectors.…”

“…With shifting of detector operation wavelength into the LWIR region, passivation issues become even more important due to reduced bandgap of detectors. A number of studies have investigated the effect of several passivation techniques on LWIR SLS detector performance employing dielectric passivation (with silicon dioxide [6], polyimide [7] or photoresist [8,9]), chalcogenide passivation (with ammonium sulfide [10] and zinc sulfide [11]), and overgrowth with larger bandgap material [12]. An elegant approach to the solution of the surface leakage current problem is the recently proposed nBn detector design [13].…”

Identification of a limiting mechanism in GaSb-rich superlattice midwave infrared detector

“…Mesa photodiodes were realized by wet-etching and the polymerized photoresist was subsequently spread onto the surface to protect the samples from ambient air. 22 Current density voltage characteristics were measured using a Keithley 6571A electrometer. The current density of samples A and B under dark conditions at 77 K is reported in Figure 2.…”