High quality mid-wavelength infrared InAs/GaSb superlattices by exploring the optimum molecular beam epitaxy growth process

• A systematic study of InAs/GaSb superlattices (SLs) epitaxial process.
• Demonstrated that As BEP has a lower limit to bring down lattice-mismatch.
• A novel shutter sequence was designed to achieve lattice matched SLs materials.
• A high quality P-I-N superlattice mid-infrared detector structure was realized.

In this paper we report on the growth of mid-wavelength infrared superlattice materials by molecular beam epitaxy. We focused on the effects of process parameters, such as arsenic beam equivalent pressure and shutter sequences, on the key material properties, such as the lattice mismatch and the surface morphology. Though a smaller As beam equivalent pressure helps to reduce the lattice mismatch between the superlattice and the GaSb substrate, the As beam equivalent pressure itself has a lower limit below which the material’s surface morphology will degrade. To achieve fully lattice-matched superlattice materials, a novel shutter sequence in the growth process was designed. With well-designed interface structures, a high quality P-I-N superlattice mid-infrared detector structure was realized. At 77 K the dark current density at −50 mV bias was 2.4 × 10−8 A/cm2 and the resistance-area product (RA) at maximum (−50 mV bias) was 2.4 × 106 Ω cm2, and the peak detectivity was then calculated to be 9.0 × 1012 cm Hz1/2/W. The background limited infrared photodetector (BLIP) level can be achieved at a temperature of 113 K.