Characterization of InSb quantum dots in InAs matrix grown by molecular beam epitaxy for infrared photodetectors

Sammanfattning: Materials for the generation and detection of long wavelength IR radiation continue to be of considerable interest for many applications such as night vision, defense and security, rescue, life sciences, industrial processing etc. For this purpose photodetection based on InSb is a well known technology in mid wavelength (3-5 μm) range. One of the ongoing projects in IMAGIC centre has been working on the development of technologies for the next generation long wavelength infrared (LWIR) photodetector focal plane arrays (FPAs) based on a ‘dot to bulk’ concept. A promising potential of this type photodetector exists to extend the detection wavelength to LWIR by using InSb QDs in InAs matrix, which also enable the device to operate at higher temperatures. Although, it is a novel and promising concept but still some challenges like optimization of material quality and device dark current etc are to be addressed. This project work has been focused on the optical and structural characterization of various size InSb QDs embedded in InAs matrix grown on InAs substrate by molecular beam epitaxy (MBE). The InSb QD’s base diameter, height and density have been revealed and evaluated by Atomic force microscopy (AFM) and transmission electron microscopy (TEM). Strong QDs related photoluminescence (PL) signals in IR range have been observed which can be attributed to interband transition between the InSb QDs (holes) and their InAs matrix (electrons). The absorption measurement results show that high absorbance is in the corresponding IR wavelength range which is in agreement with PL measurement results. The experimental results concluded from this work provide valuable information to optimize the InSb QDs materials for designing and fabricating desired LWIR photodetectors with low dark current and high photoresponsivity.