Band offset

About: Band offset is a research topic. Over the lifetime, 2446 publications have been published within this topic receiving 53450 citations.

Determination of band offsets in heterostructured colloidal nanorods using scanning tunneling spectroscopy.

Abstract: The ability to tailor the properties of semiconductor nanocrystals through creating core/shell heterostructures is the cornerstone for their diverse application in nanotechnology. The band-offsets between the heterostructure components are determining parameters for their optoelectronic properties, dictating for example the degree of charge-carrier separation and localization. So far, however, no method was reported for direct measurement of these factors in colloidal nanocrystals and only indirect information could be derived from optical measurements. Here we demonstrate that scanning tunneling spectroscopy along with theoretical modeling can be used to determine band-offsets in such nanostructures. Applying this approach to CdSe/CdS quantum-dot/nanorod core/shell nanocrystals portrays its type I band structure where both the hole and electron ground state are localized in the CdSe core, in contrast to previous reports which predicted electron delocalization. The generality of the approach is further demonstrated in ZnSe/CdS nanocrystals where their type II band alignment, leading to electron-hole separation, is manifested.

Determination of valence and conduction‐band discontinuities at the (Ga,In) P/GaAs heterojunction by C‐V profiling

Abstract: The valence and conduction band discontinuities for the lattice matched (Ga,In)P/GaAs heterojunction have been determined by capacitance‐voltage (C‐V) profiling. Both p‐p and n‐n heterojunctions were profiled, in order to obtain separate and independent values for both the valence‐band‐edge discontinuity (ΔEv) and the conduction‐band discontinuity (ΔEc). The band lineup is found to be of the straddling type with the valence‐ and conduction‐band discontinuities 0.24 and 0.22 eV, respectively, with an estimated accuracy of ±10 meV. Computer reconstruction of the C‐V profiles was used to check the consistency of the data. The band offset data indicate that the (Ga,In)P/(Al,Ga)As system should be staggered for a certain range of Al compositions.

Energy-band parameters of atomic-layer-deposition Al2O3/InGaAs heterostructure

Abstract: The valence-band offset has been determined to be 3.83±0.05eV at the atomic-layer-deposition Al2O3∕InGaAs interface by x-ray photoelectron spectroscopy. The Au–Al2O3∕InGaAs metal-oxide-semiconductor diode exhibits current-voltage characteristics dominated by Fowler-Nordheim tunneling. From the current-voltage data at forward and reverse biases, a conduction-band offset of 1.6±0.1eV at the Al2O3–InGaAs interface and an electron effective mass ∼0.28±0.04m0 of the Al2O3 layer have been extracted. Consequently, combining the valence-band offset, the conduction-band offset, and the energy-band gap of the InGaAs, the energy-band gap of the atomic-layer-deposited Al2O3 is 6.65±0.11eV.

InAs/GaSb Heterostructure Nanowires for Tunnel Field-Effect Transistors

Abstract: InAs/GaSb nanowire heterostructures with thin GaInAs inserts were grown by MOVPE and characterized by electrical measurements and transmission electron microscopy. Down-scaling of the insert thickness was limited because of an observed sensitivity of GaSb nanowire growth to the presence of In. By employing growth interrupts in between the InAs and GaInAs growth steps it was possible to reach an insert thickness down to 25 nm. Two-terminal devices show a diode behavior, where temperature-dependent measurements indicate a heterostructure barrier height of 0.5 eV, which is identified as the valence band offset between the InAs and GaSb. Three-terminal transistor structures with a top-gate positioned at the heterointerface show clear indications of band-to-band tunnelling.