Band offset

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

Low-frequency noise in strained SiGe core-shell nanowire p-channel field effect transistors

Abstract: Low-frequency noise has been studied in compressively strained Si0.8Ge0.2 core-shell nanowire (NW) p-channel transistors compared with unstrained NWs. The noise has been well interpreted using the carrier number with correlated mobility fluctuation model. The volume trap density, Nt, lies in the range of 2.9×1018–4.3×1019 cm−3 eV−1, which is similar to standard high-k planar devices. The impact of Coulomb and surface roughness scatterings is more significant in unstrained SiGe NWs. This result can be explained by the better carrier confinement at the central region of SiGe NWs due to the additional band offset in the compressively strained NWs.

Electronic structure of GaAs/AlAs symmetric superlattices: A high-pressure study near the type-I – type-II crossover

Abstract: We have measured low-temperature photoluminescence and photoluminescence excitation spectra of (GaAs${)}_{\mathrm{m}}$/(AlAs${)}_{\mathrm{n}}$ symmetric superlattices (m=n) near the type-I-to-type-II crossover under high hydrostatic pressures. For an (m,n)=(15,15) superlattice we observe a type-I band structure which becomes type II at a pressure of \ensuremath{\sim}0.22 GPa. Based on pressure coefficients, the zero-pressure splitting is extrapolated as 27(4) meV. When (m,n)=(12,12), the superlattice is type II at zero pressure, showing two luminescence bands separated by 46(4) meV which linearly diverge in energy with increasing pressure. This implies the crossover occurs when 12lm,nl15. From intensity measurements on the (m,n)=(15,15) sample, the type-I recombination rate is estimated to be 1000 times slower than scattering into the lowest-energy X-like conduction-band state. We also find the valence-band offset to be dependent on pressure. These measurements then permit us to determine the pressure coefficients of all the lowest-energy confined states relative to the AlAs-like valence band. Near crossover we see no evidence of interaction between the type-I and type-II conduction-band states.

Heteroepitaxial growth of β-LiGaO2 thin films on ZnO

Abstract: High-quality interface between an insulator and ZnO as a wide-band-gap semiconductor should realize devices based on field-effect carrier modulation or superlattices having large band offset over 1 eV. We demonstrate that LiGaO2 could be a possible candidate for this purpose. Heteroepitaxy of LiGaO2 is demonstrated on ZnO films, giving atomically sharp interface and fairly good exciton-related optical properties in the ZnO under layer. Although slight distortion of a basal-plane hexagon with a lattice mismatch of about 3% in LiGaO2 gives multidomain epitaxial structure with relaxed lattices, a possible solution is proposed to realize coherent heterointerface.

DX centres, conduction band offsets and Si-dopant segregation in ? heterostructures

Abstract: 4 K Hall measurements of MBE-grown -doped heterostructures are presented for nearly the whole composition range. The persistent photoconductivity effect is used to determine the DX level and the conduction band offset independently of each other by comparing the experimental results with self-consistent calculations. The variation of the DX level energy with composition x is found to be (eV) for x<0.38 in agreement with the negative-U model of DX centres. A ratio of conduction band to valence band offset of for x<0.38 is determined. The valence band offset is proportional to the composition x for the whole x range. We obtain the best fit for our data with (eV). Secondary ion mass spectrometry measurements reveal a strong enhancement of the Si-dopant segregation towards the surface with increasing Al concentration. The full width at half-maximum of the Si -doping layers was found to be (nm) at a growth temperature of .

Carrier Transportation Mechanism of the $\hbox{TaN}/ \hbox{HfO}_{2}/\hbox{IL}/\hbox{Si}$ Structure With Silicon Surface Fluorine Implantation

Abstract: In this paper, the current transportation mechanism of HfO2 gate dielectrics with a TaN metal gate and silicon surface fluorine implantation is investigated. Based on the experimental results of the temperature dependence of gate leakage current and Fowler-Nordheim tunneling characteristics at 77 K, we have extracted the current transport mechanisms and energy band diagrams for TaN/HfO2/IL/Si structures with fluorine incorporation, respectively. In particular, we have obtained the following physical quantities: 1) fluorinated and as-deposited interfacial layer (IL)/Si barrier heights (or conduction band offsets) at 3.2 and 2.7 eV; 2) TaN/fluorinated and as-deposited HfO2 barrier heights at 2.6 and 1.9 eV; and 3) effective trapping levels at 1.25 eV (under both gate and substrate injections) below the HfOF conduction band and at 1.04 eV (under gate injection) and 1.11 eV (under substrate injection) below the HfO2 conduction band, which contributes to Frenkel-Poole conduction.