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Principle differences between the transport properties of normal AlGaAs/InGaAs/GaAs and inverted GaAs/InGaAs/AlGaAs modulation doped heterostructures.

Prinzipielle Unterschiede der Transporteigenschaften von normalen AlGaAs/InGaAs HEMT und invertierten GaAs/InGaAs/AlGaAs modulationsdotierten Heterostrukturen
: Schweizer, T.; Ganser, P.; Köhler, K.


Applied Physics Letters 60 (1992), Nr.4, S.469-471 : Abb.,Lit.
ISSN: 0003-6951
ISSN: 1077-3118
Fraunhofer IAF ()
AlGaAs/InGaAs heterostructure; AlGaAs/InGaAs Heterostruktur; growth mechanism; InGaAs; Wachstumsmechanismus

The electrical properties of Alsub0.3Gasub0.7As/InsubxGasub1minusxAs modulation doped heterostructures grown on GaAs substrates were studied. We found for the normal and inverted heterostructures principal differences of the transport properties. For an InAs mole fraction of 0.2 the inverted modulation doped heterostructures show a stronger decrease in the electron mobility of the two- dimensional electron gas if the critical layer thickness of the Insub0.2Gasub0.8As layer is exceeded, in comparison to the normal heterostructures. This behavior can be explained by the relaxation process of the Insub0.2Gasub0.8As layer. For InsubxGasub1minusxAS heterostructures with x bigger than 0. 3 the growth mode changes from two-dimensional to threedimensional growth, which leads to interface roughness, degrading the transport properties of the normal heterostructure. Thus for high InAs mole fractions the inverted heterostructures show better transport properties in comparison to the normal heteros tructures. Low-temperature photoluminescence topography has been used to monitor local variations in composition of Insub1minusyGasubyP and AlsubxGasub1minusxAs layers which were grown lattice-matched on semi-insulating LEC GaAs substrates by MOCVD. Whereas the In content varies by less than plusminus 1 % over the whole 2 inch wafer, the Al concentration changes by about plusminus 3%.