Strong wavevector dependence of hole transport in heterostructures

Citation
G. Klimeck et al., Strong wavevector dependence of hole transport in heterostructures, SUPERLATT M, 29(3), 2001, pp. 187-216
Citations number
44
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
SUPERLATTICES AND MICROSTRUCTURES
ISSN journal
0749-6036 → ACNP
Volume
29
Issue
3
Year of publication
2001
Pages
187 - 216
Database
ISI
SICI code
0749-6036(200103)29:3<187:SWDOHT>2.0.ZU;2-A
Abstract
Heterostructures such as resonant tunneling diodes, quantum well photodetec tors and lasers, and cascade lasers break the symmetry of the crystalline l attice. Such break in lattice symmetry causes a strong interaction of heavy -, light- and split-off hole bands. A resonant tunneling diode is used as a vehicle to study hole transport in heterostructures including the subband dispersion transverse to the main transport direction. Four key findings ar e demonstrated: (I)the heavy and light hole interaction is shown to be stro ng enough to result in dominant current flow off the Gamma zone center (mor e holes flow through the structure at an angle than straight through), (2) explicit inclusion of the transverse momentum in the current integration is needed, (3) most of the current flow is due to injection from heavy holes in the emitter, and (4) the dependence on the angle phi of the transverse m omentum k is weak. Two bandstructure models are utilized to demonstrate the underlying physics: (1) independent/uncoupled heavy-, light- and split-off bands, and (2) second-nearest neigh bor sp3s* tight-binding model. Current -voltage (I-V) simulations including explicit integration of the total ener gy E, transverse momentum /k/ and transverse momentum angle phi are analyze d. An analytic formula for the current density J(k) as a function of transv erse momentum k is derived and utilized to explain the three independent me chanisms that generate off-zone-center current flow: (1) nonmonotonic (elec tron-like) hole dispersion, (2) different quantum well and emitter effectiv e masses, and (3) momentum-dependent quantum well coupling strength. The an alytic expression is also used to generate a complete I-V characteristic th at compares well to the full numerical solution. The Fermi level and temper ature dependence on the I-V is examined. Finally a simulation is compared t o experimental data. (C) 2001 Academic Press.