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Anisotropic electrical conduction in GaAs/In 0.2 Ga 0.8 As/Al 0.3 Ga 0.7 As strained heterostructures beyond the critical layer thickness.

Anisotrope elektrische Leitung in GaAs/In 0.2 Ga 0.8 As/Al 0.3 Ga 0.7 As verspannten Heterostrukturen oberhalb der kritischen Schichtdicke


Journal of applied physics 72 (1992), Nr.7, S.2941-2946 : Abb.,Lit.
ISSN: 0021-8979
ISSN: 1089-7550
Fraunhofer IAF ()
anisotrope Leitung; anisotropic conduction; cathodoluminescence; Kathodolumineszenz; strained heterostructure; verspannte Heterostruktur

The anisotropic conduction of GaAs/Insub0.2Gasub0.8As/Alsub0.3Gasub0.7As inverted high-electron-mobility transistor (HEMT) structures has been investigated. The heterostructures were grown by molecular-beam epitaxy on (100) GaAs substrates. The thickness of the pseudomorphic layer was increased stepwise (150-300 A) beyond the critical layer thickness as determined by the appearance of misfit dislocations. These mixed 60 degree dislocations surrounded by depletion regions were observed as straight dark lines in cathodoluminescence. The measured resistance RsubS was higher in the direction than in the perpendicular direction. At T equal 30 K the conduction ratio of these two directions exceeded 10high5 in the 300-A-thick layer. The magnitude and anisotropy of RsubS was correlated with the anisotropic dislocation patterns resulting from the preferential generation of the alpha dislocations as compared to the orthogonal beta dislocations. In both directions RsubS depended exponentially on the number of dark lines perpendicular to the probing current. Simultaneously, the functional form of the temperature-dependent RsubS(T) strongly varied with layer thickness. The thin, still elastically strained layers showed the usual behavior of HEMT structures.