Biperiodic superlattices and the transparent state

TL;DR

This paper investigates biperiodic semiconductor superlattices with alternating well widths, revealing how asymmetry causes band splitting and the emergence of transparent states, and explores transmission properties in semi-periodic systems.

Contribution

It provides new insights into band splitting and transparent states in asymmetric biperiodic superlattices, and analyzes transmission differences in semi-periodic configurations.

Findings

Asymmetry causes band splitting at the Bragg point.

Transparent states occur near band edges depending on well widths.

Semi-periodic systems exhibit unique transmission envelope crossing behaviors.

Abstract

Coquelin et al. studied biperiodic semiconductor superlattices, which consist of alternating cell types, one with wide wells and the other narrow wells, separated by equal strength barriers. If the wells were identical, it would be a simply periodic system of $N = 2n$ half-cells. When asymmetry is introduced, an allowed band splits at the Bragg point into two disjoint allowed bands. The Bragg resonance turns into a transparent state located close to the band edge of the lower(upper) band when the first(second) well is the wider. Analysis of this system gives insight into how band splitting occurs. Further we consider semi-periodic systems having $N= 2n+1$ half-cells. Surprisingly these have very different transmission properties, with an envelope of maximum transmission probability that crosses the envelope of minima at the transparent point.