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

Abstract

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 77K the dark current density at −50mV bias was 2.4×10−8A/cm2 and the resistance-area product (RA) at maximum (−50mV bias) was 2.4×106Ωcm2, and the peak detectivity was then calculated to be 9.0×1012cmHz1/2/W. The background limited infrared photodetector (BLIP) level can be achieved at a temperature of 113K.