In-situ Determination of the Carrier Concentration of (001) GaAs by Reflectance Anisotropy Spectroscopy (original) (raw)
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Optical measurement of carrier concentration profile in n-type semiconducting GaAs substrate
physica status solidi (a), 2007
The light absorption below the fundamental energy gap in n-type GaAs has been investigated precisely. It is experimentally confirmed that there are the three different mechanisms: (a) the enhancement of fundamental absoption due to the shrinkage of energy gap and band filling by doping Si atoms, (b) deep-level (EL2) absorption, and (c) free-carrier absorption. It is found that the transmittance measurement at the wavelength longer than about 1000 nm in the free-carrier absorption region is more useful and direct, compared with that near the fundamental absorption region from 900 nm to 950 nm, precisely to determine the carrier concentration in n-type GaAs. The two-dimensional profile of carrier concentration in a VB-grown 3 φ GaAs substrate is measured in high spatial resolution with the short time less than 5 seconds by using a sophisticated near-infrared transmittance-measuring equipment. The absolute amount and homogeneity of carrier concentration can be assessed in the range from 0.3 to 3 × 10 18 cm-3 .
Reflectance Anisotropy of GaAs(100): Theory and Experiment
Physical Review Letters, 1998
The reflectance anisotropy has been calculated by microscopic tight-binding theory for various configurations of the As-rich GaAs(100) c͑4 3 4͒ and ͑2 3 4͒ reconstructions, based on precise atomic coordinates from ab initio total-energy minimization. The comparison to experimental reflectance anisotropy in combination with scanning tunneling microscopy and low energy electron diffraction allows one to identify precise correlations between structural units and optical features. Clear indications are obtained for the intermediate steps in the surface reconstruction transformation. [S0031-9007(98)06681-2]
Ab initio calculation of the reflectance anisotropy of GaAs(110)
Physical Review B, 1998
We compute the optical properties of the ͑110͒ surface of gallium arsenide within the first-principles density-functional theory local-density approximation scheme, using norm-conserving pseudopotentials. Starting from the surface electronic structure calculation, we analyze the imaginary part of the theoretical dielectric function, separating surface and bulk contributions. The effects of the nonlocality of the pseudopotential are studied, by working both in the transverse gauge ͑neglecting them͒ and in the longitudinal gauge ͑where they are automatically included͒. The two calculations, although giving different dielectric functions, yield the same reflectance anisotropy, which compares well with experimental data and with previous theoretical results.
Journal of Crystal Growth, 1998
Using reflectance difference spectroscopy (RDS), we have obtained real-time spectroscopic data detailing the evolution of the GaAs(0 0 1) surface during metalorganic vapour phase epitaxy (MOVPE) of a single InAs monolayer (ML), and subsequent growth of a GaAs capping layer. Surface anisotropy developments were observed by recording multitransient spectra, at fixed energies from 1.5 to 4.9 eV, during the growth of 35 periods of an InAs(1 ML)/GaAs(100 A > ) superlattice (SL). From an initial d(4;4)-like GaAs surface under tertiarybutylarsine (TBAs) the RDS spectrum changes rapidly to a (2;4)-like InAs spectrum following the deposition of 1 ML of InAs. In contrast, during the growth of the GaAs cap, the evolution to the characteristic spectrum of the GaAs growing surface occurs over several monolayers, suggesting possible In segregation. Growth temperature effects were studied in a series of such samples produced at temperatures from 450°C to 600°C.
Characterization of gaas by far infrared reflectivity
Infrared Physics, 1973
We have measured the room temperature reflectivity of five samples of n-type GaAs with carrier concentrations between 5 x 1Or5 and 4 x lo'* crnm3 in the far infrared range 12-235 cm-'. The low-frequency plasmon-phonon reflectivity minimum was observed and was used to calculate values of carrier concentration and mobility which agree reasonably well with the values obtained by electrical measurements. We show a plot which may be used for rapid evaluation of the carrier concentration and mobility from the measured position and value of the minimum.