Silicon Doping Level Research Articles

Some characteristics of silicon-doped In 0.52Al 0.48As grown lattice-matched on InP substrates by molecular beam epitaxy

The characteristics of Si-doped In 0.52Al 0.48As layers as a function of the silicon doping are analyzed by low-temperature photoluminescence (PL), Raman spectroscopy and Hall effect measurements. Analysis of the PL intensity at increasing silicon doping levels showed a temperature dependence which is characteristic of disordered and amorphous materials, suggesting a behaviour which has the characteristic of disordered materials at higher doping levels. The PL linewidth broadens at higher silicon doping levels while the Raman scattering spectra showed a reduction in both the AlAs-like and InAs-like longitudinal-optic (LO) phonon frequencies coupled with a broadening of the LO phonon line shape as the doping level is increased.

Photoluminescence and raman scattering characterization of silicon-doped In0.52Al0.48As grown on InP (100) substrates by molecular beam epitaxy

Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at different silicon doping levels is carried out. The doped samples show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping levels due to a possible reduction in the donor binding energy. There is a reduction in both the AlAs-like and InAs-like longitudinal-optic (LO) phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased. The PL intensity also showed in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials.

Silicon doping in In 0.52Al 0.48As layers grown by molecular beam epitaxy: characterization of material properties

In 0.52Al 0.48As layers at different silicon doping levels are analysed by low temperature photoluminescence (PL), Raman spectroscopy and Hall effect measurements. The PL peak energy exhibits a horizontal S-shaped dependence at increasing temperature, an effect which is more prominent at lower doping levels but weakened owing to a possible reduction in the donor activation energy at higher doping levels. The frequencies of both the AlAs-like and the InAs-like longitudinal optic (LO) phonon modes decrease and the LO phonon line shape broadens as the doping level is increased. The PL intensity also showed in increasing degree, at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials. The temperature dependence of the Hall mobility exhibits clear contributions μ i and μ po from ionized impurity and polar optical phonon scattering at low and high temperatures respectively in the samples with low and moderate doping levels. Our data suggest a solubility limit of about 8 x 10 18 cm −3 for silicon doping in the InAlAs material.

Erbium Doped GaAs by Mocvd

AbstractThe overall objective of this research is to develop temperature stable 1.54 ptm light sources based upon ionic emitters. LEDs and diode lasers were fabricated in MOCVD grown AIGaAs materials but only weak electroluminescence was observed. The III-V compound semiconductors were doped with erbium amide sources of the form: Er{N[Si(CH 3)3]R}3 where R s an organic unit. These amide sources had reduced carbon and oxygen levels in a GaAs film compared to the use of a cyclopentadienyl erbium source, but did dope the semiconductor with silicon. Silicon doping levels were a function of growth temperature. Erbium photoluminescence was enhanced with oxygen codoping, but diode electrical characteristics were degraded. PLE showed that erbium ions were excited by above bandgap light absorbed by GaAs.

Photoluminescence characteristics of Si-doped In 0.52Al 0.48As grown on InP substrates by molecular beam epitaxy

The photoluminescence (PL) characteristics of Si-doped In 0.52Al 0.48As layers as a function of temperature and silicon doping level ranging from 1 × 10 17 to 4 × 10 18 cm −3 are reported. When the sample temperature is increased from 4 K, the PL peak energy exhibits an inverted S-shaped dependence which is characteristic of carrier localization. This effect was more prominent at lower doping levels but weakened at high doping levels due to a possible reduction in the donor binding energy. The peak energy variation at temperatures higher than ∼ 100 K follows the usual band-edge variation with temperature suggesting that the PL arises from band-to-band transitions, while at temperatures lower than ∼ 50 K, donor-to-band transitions are probably dominant. The PL linewidth of the undoped and moderately doped samples decreases and then increases with temperature, whereas in the highly doped samples, a near montonic increase in the linewidth due to thermal broadening was observed. In all the samples, the PL intensity showed in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials.

Some characteristics of silicon-doped In 0.52Al 0.48AS layers grown lattice-matched on InP substrates by molecular beam epitaxy

The photoluminescence (PL) characteristics of Si-doped In 0.52Al 0.48As layers as a function of temperature and silicon doping level ranging from 1 × 10 17 cm -3 to 4 × 10 18 cm -3 are reported. When the sample temperature is increased from 4 K, the PL peak energy exhibits an inverted S-shaped dependence which is characteristic of carrier localization. This effect was more prominent at lower doping levels but weakened at high doping levels due to a possible reduction in the donor binding energy. The peak energy variation at temperatures higher than ≈ 100 K follows the usual band-edge variation with temperature suggesting that the PL arises from band-to-band transitions, while at temperatures lower than ≈ 50 K, donor-to-band transitions are probably dominant. In all the samples, the PL intensity showed in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials.

The effects of substrate misorientation on silicon doping efficiency in MOVPE grown GaAs

The dependence of silicon doping level in MOVPE GaAs has been determined as a function of growth temperature and substrate crystallographic orientation. The epitaxial layers were simultaneously grown at 60 Torr from TMGa, AsH 3 and SiH 4 source materials on substrates having different orientations. Hall measurements, electrochemical profiling and SIMS were used to characterize the Si doping level and compensation ratio. The dopant incorporation was found to depend on the degree of misorientation from the (100) plane, decreasing by up to 50% for 4° off the exact (100). It was also found that this effect was strongest for growth temperatures in the 600 to 650°C range, while layers grown above 700°C exhibited no measurable orientation dependence. A dopant incorporation mechanism is advanced that is compatible with earlier theories and these new results.

Charge Exchange Mechanism Responsible for P‐Type Silicon Dissolution during Porous Silicon Formation

The anodic current‐voltage characteristics of P silicon which are obtained in electrolyte in the conditions corresponding to porous layer formation are studied in detail and analyzed according to an elementary model which accounts for the depletion layer at the silicon surface and the Helmholtz layer in the electrolyte. It is found that the determining step of silicon dissolution is the charge exchange from the bulk silicon to the semiconductor surface. This process occurs through a thermionic emission mechanism over the Schottky barrier which is formed at the silicon surface, whenever the doping level is from . Variations in the silicon doping concentration provoke a potential shift in the current‐voltage characteristics, which is almost proportional to the square root of , and which explains the selectivity of porous silicon formation vis‐a‐vis the doping level of silicon.

Amorphous-crystalline silicon heterojunction: Theoretical evaluation of the current terms

In this paper, the current mechanisms and the theoretical performance as solar cell of an amorphous-crystalline silicon heterojunction are evaluated and their dependence with the amorphous silicon doping level, the interface state density, the amorphous silicon density of gap states and the amorphous silicon gap is studied. These current terms are compared among them and with the current terms of a crystalline silicon homojunction of identical doping levels. We have found that the dominant dark current mechanism is multitunnelling across localized states of the amorphous silicon gap.

C- V curves for an amorphous/crystalline silicon heterojunction: Calculations at the static limit

In this paper the dependence of the capacitance value of the n-amorphous/ p-crystalline silicon heterojunction with the amorphous silicon doping level, the density of interface states, the density of amorphous silicon gap states and the amorphous silicon gap is studied. It is found that the capacitance depends strongly on the density of gap states and on the doping level in amorphous silicon. Values of the density of interface states that do not affect the device capacitance were estimated. This heterojunction can be used to obtain information of the amorphous silicon density of gap states parameters.

Behavior of Dopant-Related Defects in AlGaAs Superlattices

AbstractDuring the course of investigation of the mixing of highly silicon-doped GaAs/AlAs superlattices, defects such as dislocation loops and Si-rich precipitates were found to form in the specimens. These defects formed at particular doping levels upon annealing of the samples. The presence of the defects can be related to changes in mixing behavior. In the present study, transmission electron microscopy has been used to characterize the defects. Superlattices with varying silicon doping levels were annealed at different temperatures for varying time-periods, to observe the temperature-time behavior of the dislocation loops. The defects aggregate preferentially in the GaAs as opposed to the AlAs in the superlattice. A number of the dislocation-loops were investigated using high-resolution TEM. All the loops observed were interstitial in nature.

Defects Related to Mixing Behavior of Highly Silicon-Doped GaAs/AlAs Superlatitices

ABSTRACTThe mixing of highly silicon-doped GaAs/AlAs superlattices as a result of annealing has been investigated by transmission electron microscopy and secondary ion mass spectrometry. As silicon doping-levels were raised in this study to 1019 cm−3 and 1020 cm−3 defects such as prismatic dislocation loops and Si-rich precipitates were observed to occur in the superlattices upon annealing. A correlation has been observed between the presence of particular defects and the inhibition of dopant-enhanced superlattice mixing.

Fundamental limitations on DRAM storage capacitors

The evolution of the silicon dynamic RAM toward higher levels of integration has occurred primarily as a result of decreasing the size of the area in which a single bit is stored. This has been accomplished by reducing the thickness of the storage capacitor insulator, introducing higher dielectric constant materials, and increasing the silicon doping levels. Existing published data are used to explore the consequences and requirements of continuing existing density trends into the 1-4 Mb range. The results indicate that the stored charge density requirement for planar capacitors will be limited by the resultant electric field both in the insulator and silicon. These limitations are imposed by insulator conduction, tunneling, and silicon impact ionization. It is evident that for the projected stored charge density of 30 fc/μm2 for a 4-Mb DRAM, new concepts of cell design or operation must be introduced.

A study of the effects of annealing, zinc diffusion and copper diffusion on the defect structure of silicon-doped gallium arsenide

Transmission electron microscopy has been employed to study as-received, annealed, zinc-diffused and copper-diffused silicon-doped GaAs. The results on the as-received material show that the defect structure is dependent on the silicon doping level, with small perfect and faulted loops being present at high doping levels. The results of the annealing study on heavily doped material show that the size and density of the loop structure is strongly dependent on the temperature and type of loop. This behaviour has been interpreted in terms of previous work on the variation of the point-defect populations and free-carrier concentration with annealing temperature. The effect of zinc diffusion on the defect structure of heavily Si-doped GaAs has been found to be very similar to that observed after equivalent diffusions into Te-doped GaAs and is explained with reference to these results. The differences between the two cases are thought to be mainly due to the amphoteric nature of silicon in GaAs. The diffusion of copper has been found to result in large increases in the perfect and faulted loop areas. This, it is suggested, is due to the mechanism of copper diffusion in GaAs and the effect on point-defect populations of in-diffusing a p-type dopant into n-type material.

Electrical compensation in semi-insulating gallium arsenide

Boat-grown gallium arsenide doped with both silicon and chromium has been subjected to Hall effect measurements, mass spectrometry, optical and electron microscopy, and localised vibrational mode (LVM) absorption measurements. The net silicon donor concentrations ((SiGa)-(SiAs)) determined by LVM exceeded the carrier concentrations measured electrically by (1.5*1017)-1018 cm-3 depending upon the silicon doping level. These discrepancies are attributed to acceptor levels associated with the chromium. A semi-insulating crystal has been prepared with a silicon concentration of 2*1017 cm-3.

Dependence of resistivity on the doping level of polycrystalline silicon

The electrical resistivity of polycrystalline silicon films has been studied as a function of doping concentration and heat treatment. The films were grown by the chemical vapor decomposition of silane on oxidized silicon wafers. The resistivity of the as−deposited films was widely scattered but independent of dopant atom concentration at the lightly doped levels and was strong function of dopant level in the more heavily doped regions. Postdeposition heat treatments in an oxidizing atmosphere remove scatter in the data. The resultant resistivity for dopant levels less than 1016 atoms/cm3 was approximately equal to that of intrinsic silicon. In the next 2 orders of magnitude increase in dopant level, the resistivity dropped 6 orders of magnitude. A model, based on high dopant atom segregation in the grain boundaries, is proposed to explain the results.