Theory of the Electronic and Optical Properties of Semiconductor Heterostructures
Abstract
The optical spectrum of quantum wells is characterized by a series of excitonic peaks corresponding roughly to transitions between valence and conduction subband pairs subject to appropriate selection rules. In a simple model where these subbands are taken to be parabolic, the exciton spectrum for each subband pair follows a hydrogen-like series, with each exciton characterized by a two dimensional (2D) angular momentum symmetry e.g. 1s, 2s, 2p, 3d, etc. Accounting for the two types of valence subbands (heavy hole and light hole) and for the fact that only excitons with s symmetry are optically active (i.e. contribute to the oscillator strength), the excitonic transitions can then be labeled 11H(1s), 11L(1s), etc. Here, the first two indices designate the conduction and heavy (H) or light (L) hole valence subbands, respectively. For zincblende structures such as GaAs the conduction subbands can in fact be approximated accurately by parabolas. The valance subbands are, however, much more complicated because of the four-fold degeneracy of the bulk heavy and light hole valence bands at the valence band edge. This degeneracy causes the heavy and light hole subbands to be coupled resulting in the so-called valence band mixing (VBM) effects, such as 1) Strong nonparabolicities and anisotropy in the valence subband structure; 2) Magnetic field-dependent cyclotron masses; 3) Mixing of Excitons and resulting field effects on the optical absorption. (jhd)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1989
- Accession Number
- ADA214132
Entities
People
- David A. Broido
Organizations
- Boston College