Calculation of Energy Diagram of Asymmetric Graded-Band-Gap Semiconductor Superlattices

Liubomyr S Monastyrskii,Mariya P Alekseichyk,Bogdan S Sokolovskii

doi:10.1186/s11671-017-1981-4

Abstract

The paper theoretically investigates the peculiarities of energy diagram of asymmetric graded-band-gap superlattices with linear coordinate dependences of band gap and electron affinity. For calculating the energy diagram of asymmetric graded-band-gap superlattices, linearized Poisson’s equation has been solved for the two layers forming a period of the superlattice. The obtained coordinate dependences of edges of the conduction and valence bands demonstrate substantial transformation of the shape of the energy diagram at changing the period of the lattice and the ratio of width of the adjacent layers. The most marked changes in the energy diagram take place when the period of lattice is comparable with the Debye screening length. In the case when the lattice period is much smaller that the Debye screening length, the energy diagram has the shape of a sawtooth-like pattern.

Highlights

The graded-band-gap semiconductors have attracted the attention of scientists since the year 1957 when H
Kroemer puts forward the idea about quasielectric and quasimagnetic fields [1] which, in contrast with the conventional fields, act in a different way upon electrons and holes. The presence of such fields is a unique feature of semiconductors with spatially nonhomogeneous composition that leads to formation in these semiconductors in a number of properties [2] which are of interest for many practical applications, for fabrication of efficient solar cells [3, 4]
The thickness of structures can be increased without decreasing the quasielectric field intensity when one uses multilayer structures or superlattices

Summary

Introduction

The graded-band-gap semiconductors have attracted the attention of scientists since the year 1957 when H. Kroemer puts forward the idea about quasielectric and quasimagnetic fields [1] which, in contrast with the conventional fields, act in a different way upon electrons and holes The presence of such fields is a unique feature of semiconductors with spatially nonhomogeneous composition that leads to formation in these semiconductors in a number of properties [2] which are of interest for many practical applications, for fabrication of efficient solar cells [3, 4]. The features of formation of the energy diagram of graded-band-gap superlattices were established in [5, 6] for the case of the symmetric form of the latter These superlattices belong to those of a classical type [7–9] in which the superlattice’s period is much greater than the de Broglie wavelength and quantization of the energy spectra of electrons and holes does not take place. The aim of this research is to theoretically investigate the peculiarities of energy diagram of classical asymmetric graded-band-gap superlattices with linear coordinate dependences of band gap and electron affinity

Objectives

Methods

Results

Conclusion