Structural and Optical Characteristics of InAs QDs Stacked on GaAs Substrate by Molecular Beam Epitaxy

Abstract

Abstract In recent days, InAs quantum dots (QDs) photo detector is a topic of research because of their potential applications in advanced telecommunication systems and space application. The InAs QDs were grown on semi-insulating GaAs substrates by molecular beam epitaxial (MBE) System. The InAs QDs were stacked nominally with different Spacer Layer (SL) thickness of 5, 10, 15, 25 and 35 nm in order to find the optimized SL thickness. The QDs parameters like height, diameter and dot density were observed by atomic force microscopy (AFM). The QDs were approximately 4-6 nm in height, 15-25 nm in diameter and the areal density was around 3.85 x 1010 cm-2 for 2.4 mono layers (MLs) of single layer QDs grown at 500°C. The photoluminescence (PL) spectra of single layer InAs QDs covered by GaAs layer centered at 1079 nm. For less SL thickness (5, 10 nm) the peak position was red shifted to 1100 nm due to size broadening of QDs. For SL thickness of 35 nm the peak position was around 1084 nm which is almost near to the single layer QDs. The six layers stacked InAs QDs structure was examined by using scanning tunneling microscope (STM) and transmission electron microscope (TEM) to determine the QDs parameters and thickness of the grown layers. The structural and optical characterizations will be discussed in detail.