Atomic-Scale Characterization of II–VI Compound Semiconductors

Abstract

Alloys of II-VI compound semiconductors with suitable band gap selection potentially provide broad coverage of wavelengths for photodetector applications. Achievement of high-quality epitaxial growth is, however, essential for successful development of integrated photonic and optoelectronic devices. Atomic-scale characterization of structural defects in II-VI heterostructures using electron microscopy plays an invaluable role in accomplishing this goal. This paper reviews some recent high-resolution studies of II-VI compound semiconductors with zincblende crystal structure, as grown epitaxially on commonly used substrates. Exploratory studies using aberration-corrected electron microscopes are also briefly considered.

Atomic-Resolution Structure Imaging of Misfit Dislocations at Heterovalent II–VI/III–V Interfaces

“…Semiconductor superlattices and heterostructures based on compound semiconductors have provided major breakthroughs for the electronics and optoelectronics industries, including the fabrication of devices such as light-emitting diodes, quantum-well infrared photodetectors, and quantum cascade lasers . Research involving these material systems has focused primarily on either isovalent heterostructures where both materials have the same valence or structures where a compound semiconductor is grown on an elemental semiconductor, such as GaAs on Si. − Heterovalent structures, achieved, for example, by integrating II–VI and III–V compound semiconductors with different valence states, provide many possibilities for further developments in optoelectronic devices. , For example, a combination of II–VI/III–V materials could enable multijunction solar cells that access a wider range of the solar energy spectrum. , Moreover, the interfaces between heterovalent materials have bonding mismatch that may provide further opportunities arising from the introduction of interfacial electrostatic dipoles; for instance, a recent theoretical paper proposed the existence of a two-dimensional electron gas at the CdTe(111)/InSb(111) polar interface …”

The Relationship Between Atomic Structure and Strain Distribution of Misfit Dislocation Cores at Cubic Heteroepitaxial Interfaces

“…Semiconductor heteroepitaxial films with cubic diamond or zincblende structure grown on (001)-oriented substrates have been studied for a long time (Gosling, 1993; Narayan & Oktyabrsky, 2002; Bolkhovityanov et al, 2011; Smith, 2013). Misfit dislocations (MDs) are rapidly generated at heteroepitaxial interfaces, particularly with large lattice mismatch, to relieve misfit strain.…”

“…Misfit dislocations (MDs) are rapidly generated at heteroepitaxial interfaces, particularly with large lattice mismatch, to relieve misfit strain. These MDs commonly include Lomer dislocations (LDs), 60° dislocations, and closely spaced 60° dislocation pairs (Vila et al, 1995, 1996; Narayan & Oktyabrsky, 2002; Wang et al, 2011, 2012; Smith, 2013). The atomic structure of MD cores is very important for analyzing the MD formation mechanism and the related interfaces (Narayan & Oktyabrsky, 2002; Bolkhovityanov et al, 2011, 2013; Wang et al, 2012).…”