Nature of Growth Pits in Lead Salt Epilayers Grown by Molecular Beam Epitaxy

Abstract

We present a detailed study on the surface morphologies and chemical composition of growth pits in lead selenide (PbSe) epilayers grown by molecular-beam epitaxy. Various growth pits were investigated by scanning electron microscopy and energy-dispersive x-ray analysis. The vast majority of growth pits within the PbSe epilayers contained either single or multiple PbSe microcrystals with a distinct cuboid shape. Based on the observed structures and morphologies of the PbSe microcrystals, the formation mechanism of the cuboid structures was considered to be (100) preferential crystal growth originating from PbSe polycrystalline seeds.

Recent development on the uncooled mid-infrared PbSe detectors with high detectivity

“…[17] Lead salt semiconductors have a distinct nature of self-crystallization -nucleation/formation of high quality micro-size monocrystalline materials without transferring the mismatch information from the substrate. Such self-crystallized single crystals were also found in lead salt epitaxial films, which were previously portrait as growth pits [18] as is shown in figure 3. Transmission electron microscopy (TEM) study shows that these self-crystallized cuboids have very high crystal quality with no dislocation observed, as shown in figure 4.…”

A new in-situ surface treatment during MBE-grown PbSe on CaF2/Si(111) heterostructure

“…There have been studies on the threading dislocations in IV-VI semiconductors [4,5]. The growth pits in the IV-VI semiconductors, however, have not been intensively studied until recently by our research group [6]. We found that the majority of growth pits within the PbSe epilayers contain either single or multiple PbSe micro-crystals with a distinct cuboid shape.…”

Growth mechanism of cuboid growth pits in lead selenide epilayers grown by molecular beam epitaxy

“…A few large cuboid growth pits of various shapes and a number of smaller defects, ranging from less than one-half to several micrometres in size are present. The plan-view SEM image, figure 1(b), shows that the large growth pits are composed of multiple-faceted features with cubic symmetry and have been named 'PbSe cuboids' [9]. These cuboids are typically found as single cubes, but also form larger conglomerates of multiple cubes.…”

“…Recently, much effort has been devoted to improving material quality and understanding the formation of dislocations and other growth defects in IV-VI materials [7][8][9]. It was found that one prevalent type of growth defect in molecular beam epitaxy (MBE) grown PbSe epitaxial layers, the so-called 'cuboid growth pits', was composed of single or multiple micrometre-sized PbSe crystals with their geometric structures embedded in the PbSe (1 1 1) epilayers [9]. For the prevailing II-VI and III-V materials such as Hg 1−x Cd x Te and In 1−x Ga x As, the formation of various growth defects such as twins, craters, hillocks and V-shaped defects has been intensively studied and different models have been proposed to explain the growth mechanisms [10][11][12].…”

“…Recently, much effort has been devoted to improving material quality and understanding the formation of dislocations and other growth defects in IV-VI materials [7][8][9]. It was found that one prevalent type of growth defect in molecular beam epitaxy (MBE) grown PbSe epitaxial layers, the so-called 'cuboid growth pits', was composed of single or multiple micrometre-sized PbSe crystals with their geometric structures embedded in the PbSe (1 1 1) epilayers [9].…”