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Effective mass (solid-state physics)

About: Effective mass (solid-state physics) is a research topic. Over the lifetime, 12539 publications have been published within this topic receiving 295485 citations.


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TL;DR: In this article, the electronic band structures of bulk Ge1-xSnx alloys were investigated using the empirical pseudopotential method (EPM) for Sn composition x varying from 0 to 0.2.
Abstract: This work investigates the electronic band structures of bulk Ge1-xSnx alloys using the empirical pseudopotential method (EPM) for Sn composition x varying from 0 to 0.2. The adjustable form factors of EPM were tuned in order to reproduce the band features that agree well with the reported experimental data. Based on the adjusted pseudopotential form factors, the band structures of Ge1-xSnx alloys were calculated along high symmetry lines in the Brillouin zone. The effective masses at the band edges were extracted by using a parabolic line fit. The bowing parameters of hole and electron effective masses were then derived by fitting the effective mass at different Sn compositions by a quadratic polynomial. The hole and electron effective mass were examined for bulk Ge1-xSnx alloys along specific directions or orientations on various crystal planes. In addition, employing the effective-mass Hamiltonian for diamond semiconductor, band edge dispersion at the Γ-point calculated by 8-band k.p. method was fitted...

198 citations

Journal ArticleDOI
TL;DR: In this paper, the lifetime of excess charge carriers in GaN epitaxial layers grown on sapphire at temperatures up to 300 K was measured by using picosecond time-resolved photoluminescence.
Abstract: By using picosecond time-resolved photoluminescence we have measured the lifetime of excess charge carriers in GaN epitaxial layers grown on sapphire at temperatures up to 300 K. The decay time turns out to be dominated by trapping processes at low excitation levels. The radiative lifetime derived from our data is dominated by free excitons at temperatures below 150 K, but also clearly shows the gradual thermal dissociation of excitons at higher temperatures. From our data, we are able to determine the free exciton binding energy and the free carrier radiative recombination coefficient. By combining these data with optical absorption data, we find the interband momentum matrix element and an estimate for the hole effective mass, which is much larger than previously thought.

197 citations

Journal ArticleDOI
TL;DR: It is shown that the combination of unusual features specific to semimetals gives rise to a unique ordering and spacing of three characteristic energy scales, which not only is specific toSemimetals but which concomitantly provides a wide window for the observation of apparent field-induced metal-insulator behavior.
Abstract: When high quality bismuth or graphite crystals are placed in a magnetic field directed along the c axis (trigonal axis for bismuth) and the temperature is lowered, the resistance increases as it does in an insulator but then saturates. We show that the combination of unusual features specific to semimetals, i.e., low carrier density, small effective mass, high purity, and an equal number of electrons and holes (compensation), gives rise to a unique ordering and spacing of three characteristic energy scales, which not only is specific to semimetals but which concomitantly provides a wide window for the observation of apparent field-induced metal-insulator behavior. Using magnetotransport and Hall measurements, the details of this unusual behavior are captured with a conventional multiband model, thus confirming the occupation by semimetals of a unique niche between conventional metals and semiconductors.

197 citations

Journal ArticleDOI
TL;DR: In this paper, the first calculations of hole initiated interband impact ionization in bulk zincblende and wurtzite phase GaN are presented using an ensemble Monte Carlo simulation including full details of all of the relevant valence bands, derived from an empirical pseudopotential approach, for each crystal type.
Abstract: In this article, the first calculations of hole initiated interband impact ionization in bulk zincblende and wurtzite phase GaN are presented. The calculations are made using an ensemble Monte Carlo simulation including the full details of all of the relevant valence bands, derived from an empirical pseudopotential approach, for each crystal type. The model also includes numerically generated hole initiated impact ionization transition rates, calculated based on the pseudopotential band structure. The calculations predict that both the average hole energies and ionization coefficients are substantially higher in the zincblende phase than in the wurtzite phase. This difference is attributed to the higher valence band effective masses and equivalently higher effective density of states found in the wurtzite polytype. Furthermore, the hole ionization coefficient is found to be comparable to the previously calculated electron ionization coefficient in zincblende GaN at an applied electric field strength of 3 MV/cm. In the wurtzite phase, the electron and hole impact ionization coefficients are predicted to be similar at high electric fields, but at lower fields, the hole ionization rate appears to be greater.

197 citations

Journal ArticleDOI
TL;DR: In this paper, the electronic structure and transmission coefficients of Si nanowires were calculated in a sp/sup 3/d/sup 5/s/sup model, and the effect of wire thickness on the bandgap, conduction valley splitting, hole band splitting, effective masses, and transmission was demonstrated.
Abstract: The electronic structure and transmission coefficients of Si nanowires are calculated in a sp/sup 3/d/sup 5/s/sup */ model. The effect of wire thickness on the bandgap, conduction valley splitting, hole band splitting, effective masses, and transmission is demonstrated. Results from the sp/sup 3/d/sup 5/s/sup */ model are compared to those from a single-band effective mass model to assess the validity of the single-band effective mass model in narrow Si nanowires. The one-dimensional Brillouin zone of a Si nanowire is direct gap. The conduction band minimum can split into a quartet of energies although often two of the energies are degenerate. Conduction band valley splitting reduces the averaged mobility mass along the axis of the wire, but quantum confinement increases the transverse mass of the conduction band edge. Quantum confinement results in a large increase in the hole masses of the two highest valence bands. A single-band model performs reasonably well at calculating the effective band edges for wires as small as 1.54-nm square. A wire-substrate interface can be viewed as a heterojunction with band offsets resulting in reflection in the transmission.

196 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202215
2021410
2020421
2019395
2018362
2017412