Material and device characterization of Type-II InAS/GaSb superlattice infrared detectors

TL;DR

This study characterizes Type-II InAs/GaSb superlattice infrared detectors grown by molecular beam epitaxy, exploring different interface engineering methods to improve structural, optical, and device performance for midwave infrared applications.

Contribution

It introduces a novel interface engineering approach using antimony-for-arsenic exchange to achieve nearly strain-compensated superlattices with improved surface and optical properties.

Findings

Achieved nearly strain-compensated superlattice with 56 arcsec FWHM.

Produced smooth surface with 0.19 nm RMS roughness.

Demonstrated a p-i-n detector with 5.15 μm cutoff wavelength and low dark current.

Abstract

This work investigates midwave infrared Type-II InAs/GaSb superlattice (SL) grown by molecular beam epitaxy on GaSb substrate. In order to compensate the natural tensile strain of the InAs layers, two different shutter sequences have been explored during the growth. The first one consists of growing an intentional InSb layer at both interfaces (namely GaSb-on-InAs and InAs-on-GaSb interfaces) by migration enhanced epitaxy while the second uses the antimony-for-arsenic exchange to promote an InSb-like interface at the GaSb-on-InAs interface. SLs obtained via both methods are compared in terms of structural, morphological and optical properties by means of high-resolution x-ray diffraction, atomic force microscopy and photoluminescence spectroscopy. By using the second method, we obtained a nearly strain-compensated SL on GaSb with a full width at half maximum of 56 arcsec for the first-order SL satellite peak. Relatively smooth surface has been achieved with a root mean square value of about 0.19 nm on a 2 $\mu m$ x 2 $\mu m$ scan area. Finally, a p-i-n device structure having a cut-off wavelength of 5.15 $\mu m$ at 77K has been demonstrated with a dark-current level of $8.3 * 10^{-8} A/cm^2$ at -50 mV and a residual carrier concentration of $9.7 * 10^{14} cm^{-3}$, comparable to the state-of-the-art.