The effect of thermal and structural disorder on the electronic structure hydrogenated amorphous silicon is investigated by measurement shape optical absorption edge as a function temperature evolution hydrogen. data are consistent with idea that additive, suggest disorder, rather than hydrogen content, fundamental determining factor in band gap.

The detailed balance method for calculating the radiative recombination limit to performance of solar cells has been extended include free carrier absorption and Auger in addition losses. This applied crystalline silicon where limiting efficiency is found be 29.8 percent under AM1.5, based on measured optical spectrum published values coefficients. assumed textured maximum benefit from light-trapping effects.

The width of the conduction- and valence-band tails in amorphous silicon hydride are inferred from time-of-flight measurements temperature dependence electron hole drift mobilities, a multiple-trapping model dispersive transport.

A new class of semiconductor superlattice materials consisting alternating layers 8-1200-\AA{} thick has been synthesized from semiconductors such as $a\ensuremath{-}\mathrm{Si}:\mathrm{H}$, $a\ensuremath{-}\mathrm{Ge}:\mathrm{H}$, $a\ensuremath{-}\mathrm{Si}{\mathrm{N}}_{x}:\mathrm{H}$, and $a\ensuremath{-}{\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{C}}_{x}:\mathrm{H}$. X-ray diffraction, photoconductivity, photoluminescence measurements indicate that the are smooth on an atomic scale,...

GaAs 1−x Bi x epilayers with bismuth concentrations up to x=3.1% were grown on by molecular beam epitaxy. The content in the films was measured Rutherford backscattering spectroscopy. X-ray diffraction shows that GaAsBi is pseudomorphically strained but some structural disorder present thick films. extrapolation of lattice constant hypothetical zincblende GaBi alloy gives 6.33±0.06 Å. Room-temperature photoluminescence obtained and a significant redshift emission ∼84 meV per percent observed.

We report a giant bowing of the spin-orbit splitting energy ${\ensuremath{\Delta}}_{0}$ in dilute ${\mathrm{GaAs}}_{1\ensuremath{-}x}{\mathrm{Bi}}_{x}$ alloy for Bi concentrations ranging from 0% to 1.8%. This is first observation large relativistic correction host electronic band structure induced by just few percent isoelectronic doping semiconductor material. It opens up possibility tailoring semiconductors spintronic applications.

The GaBixAs1−x bismide III-V semiconductor system remains a relatively underexplored alloy particularly with regards to its detailed electronic band structure. Of particular importance understanding the physics of this is how bandgap energy Eg and spin-orbit splitting Δo vary relative one another as function Bi content, since in it becomes possible for exceed higher fractions, which occurrence would have important implications minimising non-radiative Auger recombination losses such...

Room temperature photoluminescence (PL) spectra have been measured for GaAs1−xBix alloys with Bi concentrations in the 0.2%–10.6% range. The decrease PL peak energy increasing concentration follows reduction bandgap computed from density functional theory. is found to increase pump intensity, which we attribute presence of shallow localized states associated clusters near top valence band. intensity at low concentrations, peaking 4.5% Bi.

We describe how the Bi content of GaAs1−xBix epilayers grown on GaAs can be controlled by growth conditions in molecular beam epitaxy. Nonstandard are required because strong tendency for to surface segregate under usual GaAs. A maximum 10% is achieved at low substrate temperature and arsenic pressure, as inferred from x-ray diffraction measurements. model bismuth incorporation proposed that fits a large body experimental data wide range conditions. Low rates found facilitate bismide alloys...

The incorporation of Bi is investigated in the molecular beam epitaxy growth GaAs1−xBix. content increases rapidly as As2:Ga flux ratio lowered to 0.5 and then saturates for lower ratios. Growth under Ga rich conditions shows that strongly with decreasing temperature. A model proposed where from a wetting layer incorporates through attachment Ga-terminated surface sites. weak Ga-Bi bond can be broken thermally, ejecting back into layer. Highly crystalline films up 22% were grown at...

The photoluminescence from a Ga(AsBi) sample is investigated as function of pump power and lattice temperature. disorder-related features are analyzed using Monte Carlo simulation technique. A two-scale approach introduced to separately account for cluster localization alloy disorder effects. corresponding characteristic energy scales 11 45 meV deduced the detailed comparison between experiment simulation.

Low-temperature (LT) grown GaAs has a subpicosecond carrier response time that makes it favorable for terahertz photoconductive (PC) switching. However, this is obtained at the price of lower mobility and thermal conductivity than GaAs. Here we demonstrate sweep-out over an order magnitude higher sensitivity in detection from GaAs-based PC switch by using nanoplasmonic structure. As compared to conventional switch, observe 40 times peak-to-peak structure on The double commercial,...

Recombination mediated by band tail states is shown to substantially reduce the maximum achievable output voltage in amorphous silicon hydride solar cells. The open circuit calculated from measured density of parameters and reasonable estimates for localized state capture rates 1.0±0.1 V.

We investigate the electronic properties of GaAs1−xBix by photoluminescence at variable temperature (T=10–430K) and high magnetic field (B=0–30T). In GaAs0.981Bi0.019, localized state contribution to PL is dominant up 150K. At T=180K diamagnetic shift free-exciton states reveals a sizable increase in carrier effective mass with respect GaAs. Such an cannot be accounted for enhanced character valence band states, solely. Instead, it suggests that also Bloch conduction are heavily affected...

The size and distribution of built-in electric fields in $a\ensuremath{-}\mathrm{Si}:\mathrm{H}/a\ensuremath{-}\mathrm{Si}{\mathrm{N}}_{x}:\mathrm{H}$ layered amorphous semiconductor materials have been determined by use electroabsorption spectroscopy. Strong asymmetries are present between the interfaces, leading to internal as large 4 \ifmmode\times\else\texttimes\fi{} ${10}^{5}$ V/cm material with thin (12 \AA{}) layers. These due an interface charge when silicon is deposited onto...

In this review we describe the growth and properties of dilute bismide semiconductor alloy GaAs1−xBix show how its are in certain respects complementary to nitride alloy, GaNyAs1−y. Like nitrides bismides a giant band gap bowing effect which small concentration alloying element has disproportionate on gap, however case reduction is associated with an increase energy valence maximum (VBM) rather than conduction minimum (CBM). Under standard GaAs conditions Bi acts as surfactant improvements...

The electron drift mobility μd was measured in hydrogenated a-Si films prepared by rf and dc glow discharge silane reactive sputtering an Ar-H2 gas mixture. transport the glow-discharge material found to be nondispersive. highest observed room-temperature mobility, 0.8 cm2/V s, is a factor of 8 higher than previously reported. An 0.05 s sputtered material.

We investigate the temperature and pressure dependence of light-current characteristics electroluminescence spectra GaAs1−xBix/GaAs light emitting diodes. The emission wavelength shows a relatively low coefficient peak shift 0.19 ± 0.01 nm/K. A strong decrease in efficiency with increasing implies that non-radiative recombination plays an important role on performance these devices. GaAs0.986Bi0.014 bandgap is measured to be 11.8 0.3 meV/kbar. intensity from GaAsBi found accompanied by...

We use plasmon enhancement to achieve terahertz (THz) photoconductive switches that combine the benefits of low-temperature grown GaAs with mature 1.5 μm femtosecond lasers operating below bandgap. These bandgap plasmon-enhanced receivers and sources significantly outperform commercial devices based on InGaAs, both in terms bandwidth power, even though they operate well saturation. This paves way for high-performance low-cost portable systems enable emerging THz applications spectroscopy,...

The compositional dependence of the fundamental bandgap pseudomorphic GaAs1−xBix layers on GaAs substrates is studied at room temperature by optical transmission and photoluminescence spectroscopies. All films (0 ≤ x 17.8%) show direct bandgaps, which decrease with increasing Bi content, closely following density functional theory predictions. smallest measured 0.52 eV (∼2.4 μm) 17.8% Bi. Extrapolating a fit to data, predicted reach 0 35% Below bandgap, exponential absorption band tails are...

Arrayed hexagonal metal nanostructures are used to maximize the local current density while providing effective thermal management at nanoscale, thereby allowing for increased emission from photoconductive terahertz (THz) sources. The THz field amplitude was by 60% above that of a commercial antenna, even though nanostructured device had 75% bias voltage. arrayed outperforms our previously investigated strip array nanoplasmonic structure stronger localization near surface with an operating...