Band offset

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

Self-consistent dipole theory of heterojunction band offsets

Abstract: A theory of heterojunction band offsets is developed within the density-functional framework in the local-density approximation. The linear-muffin-tin-orbital method is used in conjunction with a superlattice geometry for solving Schr\"odinger's equation of the heterojunction. The potential is constructed within the atomic-sphere approximation. Within this context the long-range electrostatics reduce to that of point charges, and the average electrostatic potential of the latter can be used as a local reference level. It is shown that, starting from an arbitrary alignment of the bulk potentials, the correct potential alignment is obtained by minimizing the total energy with respect to a single parameter: the interface dipole. This minimization is equivalent to screening the initially induced dipole by the macroscopic dielectric constant of the interface region of the heterojunction, which can be identified approximately with the harmonic average of the dielectric constants of the two semiconductors. The conditions under which this is valid are discussed. The calculations are performed within a so-called frozen-shape approximation, allowing the potentials to vary only by constant shifts. Almost perfect agreement between calculations using a different shift per atomic layer and calculations using a single shift per semiconductor provide a numerical demonstration that the self-consistent dipole is independent of the details of the dipole profile. They also show that the macroscopic dielectric constant of the heterojunction in the vicinity of the interface can be obtained with reasonable accuracy from the single-parameter variational calculation itself. The calculations also show that linear response is valid over a wide range. The theory is applied to an extensive set of lattice-matched semiconductor (110) interfaces and shown to be in excellent agreement with experimental results and previous more-involved calculations where available. The consequences of the present theory for interface-orientation dependence and metal-semiconductor interfaces are briefly discussed.

Valence band offset of InN∕AlN heterojunctions measured by x-ray photoelectron spectroscopy

Abstract: The valence band offset of wurtzite-InN∕AlN (0001) heterojunctions is determined by x-ray photoelectron spectroscopy to be 1.52±0.17eV. Together with the resulting conduction band offset of 4.0±0.2eV, a type-I heterojunction forms between InN and AlN in the straddling arrangement.

A dielectric-defined lateral heterojunction in a monolayer semiconductor

Abstract: Owing to their low dimensionality, two-dimensional semiconductors, such as monolayer molybdenum disulfide, have a range of properties that make them valuable in the development of nanoelectronics. For example, the electronic bandgap of these semiconductors is not an intrinsic physical parameter and can be engineered by manipulating the dielectric environment around the monolayer. Here we show that this dielectric-dependent electronic bandgap can be used to engineer a lateral heterojunction within a homogeneous MoS2 monolayer. We visualize the heterostructure with Kelvin probe force microscopy and examine its influence on electrical transport experimentally and theoretically. We observe a lateral heterojunction with an approximately 90 meV band offset due to the differing degrees of bandgap renormalization of monolayer MoS2 when it is placed on a substrate in which one segment is made from an amorphous fluoropolymer (Cytop) and another segment is made of hexagonal boron nitride. This heterostructure leads to a diode-like electrical transport with a strong asymmetric behaviour. A lateral heterojunction with diode-like electrical transport can be created in a homogeneous MoS2 monolayer by using a substrate in which one segment is made from an amorphous fluoropolymer and another segment from hexagonal boron nitride.

Band gap and band discontinuities at crystalline Pr2O3/Si(001) heterojunctions

Abstract: We report the experimental results on the band alignment of Pr2O3 films on Si(001) as prepared by molecular beam epitaxy Using x-ray photoelectron spectroscopy, we obtain a valence band offset at the Pr2O3/Si(001) interface of (11±02) eV High field tunneling was used to extract the conduction band offset of (05–15) eV Thus, the Pr2O3/Si(001) interface band alignment is symmetric, desired for applying such materials in both n- and p-type devices The band gap of bulk Pr2O3 should be between 25 and 39 eV Using scanning tunneling spectroscopy, we find a surface-state band gap of about 32 eV for monolayer coverage In agreement with recent pseudopotential calculations, the electron masses in the oxide appear to be very large This effect, together with the suitable band offsets lead to the unusually low leakage currents recently measured