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Measurement of heterojunction band offsets using ballistic electron emission microscopy
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1994
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Wide-bandgap SemiconductorEngineeringElectron-beam LithographyMicroscopyElectron DiffractionOptoelectronic DevicesSemiconductorsElectronic DevicesElectron MicroscopyElectron SpectroscopyQuantum MaterialsInstrumentationMolecular Beam EpitaxySemiconductor TechnologyElectrical EngineeringCrystalline DefectsPhysicsSemiconductor HeterostructuresSchottky BarrierSemiconductor MaterialApplied PhysicsHeterojunction Band OffsetsElectron MicroscopeMultilayer Heterostructures
Ballistic electron emission microscopy (BEEM) has been used to study electron transport across single barrier AlxGa1−xAs/GaAs heterostructures. The structures, grown by molecular beam epitaxy, utilized a p-type δ-doped sheet to cancel the band bending near the Schottky interface, enabling a direct measurement of the conduction band offset at room temperature. The band offset at room temperature for x=0.21 is 0.19 eV and for x=0.42 is 0.33 eV. Measurements at 77 K gave values of 0.20 eV for x=0.21 and 0.35 eV for x=0.42. These results demonstrate that BEEM can be used to probe the transport properties of semiconductor heterostructures which are spatially beneath the Schottky barrier.