Molecular beam epitaxy of ZnSSe/CdSe short-period superlattices for III–V/II–VI multijunction solar cells

Abstract

Results on the molecular beam epitaxy growth of short period alternately strained ZnS x Se 1 -x /CdSe superlattices which are pseudomorphic to GaAs (001) substrates and possess effective band gap values within the range of E g ≈ 2.5-2.7 eV are presented. Oscillations of the specular spot intensity in reflection high energy electron diffraction are used for in situ control of the superlattice parameters. A method to determine the SL parameters (compositions and thicknesses of the constituent layers) based on combined analysis of the grown structures by low temperature photoluminescence and X ray diffractometry is developed. It is found that the parameters of the grown ZnS x Se 1 -x /CdSe superlattices are close to their design values and the den sity of extended defects in the structures is low even though the structure thickness (~300 nm) considerably exceeds the critical thickness for bulk II-VI layers with the same lattice constant mismatch.

Carrier Scattering at Alloy Nanointerfaces Enhances Power Factor in PEDOT:PSS Hybrid Thermoelectrics

“…28−32 For example, scientists have carefully grown 1D superlattices using molecular beam epitaxy. 31,32 These structures provide an important proof of principle for precise tuning of energetic and optical properties in 1D systems but are limited by high costs and lack of scalability. Alternatively, inclusion of nanoparticles in a matrix of thermoelectric material has been successfully used to improve thermoelectric performance, but this route suffers from insufficient control over the resulting interfaces and nanoparticle dispersion.…”

“…One-dimensional (1D) nanowires are advantageous because they feature relaxed epitaxy, and physics can be directly interrogated on a single nanowire basis. A host of well-explored vapor-phase deposition techniques exist for precise patterning of 1D nanostructures. − For example, scientists have carefully grown 1D superlattices using molecular beam epitaxy. , These structures provide an important proof of principle for precise tuning of energetic and optical properties in 1D systems but are limited by high costs and lack of scalability. Alternatively, inclusion of nanoparticles in a matrix of thermoelectric material has been successfully used to improve thermoelectric performance, but this route suffers from insufficient control over the resulting interfaces and nanoparticle dispersion. − Instead, what is required is engineering of target materials with well-defined interfaces and energetics.…”

Photovoltaic performance of an alternating cold–hot method deposited CdSe thin films

“…However, the cubic structure is unstable and converts to the hexagonal form as the annealing temperature reaches 520°C [13]. There are several methods to prepare CdSe thin films such as thermal evaporation [14][15][16], electrodeposition [17][18][19], molecular beam epitaxy [20][21][22], chemical bath deposit [23][24][25], sol-gel method [26,27] and hydrothermal method [28][29][30]. Recently, chemical bath deposit method is very popular because the thickness, chemical compositions and structure of the CdSe thin films are much easier to control.…”