Theory of tunneling in semiconductor heterostructures

Miscellaneous · Wed Jan 01 00:00:00 EST 1992

OSTI ID:7071977

Sankaran, V

Advances in material growth technology and ultrafast spectroscopic techniques have stimulated a great deal of investigation into the static and dynamic aspects of tunneling in semiconductor heterostructures. The existing theory of tunneling in solids is inadequate to model such tunneling processes in all their complexity. In this thesis, a new theoretical formalism is developed wherein tunneling properties are determined by studying the time evolution of localized wavepackets. Their time evolution is determined by a direct numerical solution of the time-dependent Schroedinger equation, using a unitary approximation of the evolution operator. The procedure is applicable to any multi-band representation of electronic states in heterostructures. It fully retains the band mixing aspects and symmetries of the underlying basis states. It is well suited to study the dynamics of tunneling in the presence of space and time-dependent electric field profiles. This technique was applied to investigate resonant tunneling of holes between localized states in coupled quantum wells, employing the Luttinger representation for degenerate valence bands. An issue of some controversy in reports of experiments on this structure was the role of heavy hole (HH)-light hole (LH) coupling in resonances induced by an external electric field. It was found that tunneling between HH and LH states is suppressed only for zero in-plane wavevector, and is quite rapid otherwise. But this coherent tunneling may be observed experimentally only in the presence of an appropriate relaxation mechanism, which could vary between experiments. The formalism was applied to explore the role of [Gamma]-point and X-point states in electron tunneling through indirect bandgap Al[sub x]Ga[sub 1[minus]x]As barriers, employing the tight-binding representation for electronic states. The tunneling lifetime was found to depend exponentially on barrier thickness.

• Research Organization: Michigan Univ., Ann Arbor, MI (United States)
• OSTI ID: 7071977
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SCHROEDINGER EQUATION
NUMERICAL SOLUTION
SEMICONDUCTOR MATERIALS
TUNNEL EFFECT
ALUMINIUM ARSENIDES
GALLIUM ARSENIDES
ALUMINIUM COMPOUNDS
ARSENIC COMPOUNDS
ARSENIDES
DIFFERENTIAL EQUATIONS
EQUATIONS
GALLIUM COMPOUNDS
MATERIALS
PARTIAL DIFFERENTIAL EQUATIONS
PNICTIDES
WAVE EQUATIONS
665000* - Physics of Condensed Matter- (1992-)
665411 - Basic Superconductivity Studies- (1992-)