Optical measurement of carrier concentration profile in n-type semiconducting GaAs substrate (original) (raw)
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Effect of the Doping Layer Concentration on Optical Absorption in Si δ-Doped GaAs Layer
Optics and Photonics Journal, 2012
We study in this paper the intersubband optical absorption of Si- doped GaAs layer for different applied electric fields and donors concentration. The electronic structure has been calculated by solving the Schrödinger and Poisson equations self-consistently. From our results, it is clear that the subband energies and intersubband optical absorption are quite sensitive to the applied electric field. Also our results indicate that the optical absorption depends not only on the electric field but also on the donor's concentration. The results of this work should provide useful guidance for the design of optically pumped quantum well lasers and quantum well infrared photo detectors (QWIPs).
physica status solidi (a), 2001
We demonstrate the use of Reflectance Anisotropy Spectroscopy (RAS) to determine the carrier concentration in GaAs of the topmost layers (%20 nm) in-situ during layer growth. The doping contributes to three features in the RAS spectra: an oscillation at E 1 =E 1 þ D 1 , an oscillation at E 0 0 =E 0 0 þ D 0 0 and an offset of the baseline of the whole spectrum. Using the empirical calibration in this paper, carrier concentrations above % 10 17 cm À3 can be easily measured by RAS for a given temperature, dopant and reconstruction.
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.
Optical characterization of ultra-pure GaAs
physica status solidi (c), 2003
The problem of ultra-pure thick GaAs layers has been important for a long time. Growth of such material is an important technological problem and the basis of application in electronic devices. Epitaxial (100 -1000) µm thick GaAs layers were grown by vapour phase epitaxy in a chloride system (HVPE) on N + and semi insulating 2″ substrates horizontally; the growth zone extended over ∼19 cm with a temperature gradient of ∼3 °C/cm. The total impurity concentration N was in the range ≤ 10 12 -10 14 cm -3 . These epilayers have been investigated using low temperature photoluminescence (LTPL), C -V, and Hall measurements. However, estimation of the electro-physical parameters of ultra-pure (N ≤ 10 12 cm -3 ) GaAs often causes difficulties. Because of the low concentration of impurities (N ≤ 10 12 cm -3 ) electro-physical measurements are difficult in many cases or even impossible. In those cases where electro-physical measurements proved feasible a direct relationship was established between the variation of the electrophysical parameters and the evolution of the LTPL spectra at 2 K. By extrapolating the obtained data to regions of lower impurity concentration, N D and µ e values corresponding to certain values of the parameters of the LTPL spectra could be found. Thus, analysis of the LTPL spectra can yield estimates of N D and µ e when direct determination is difficult or impossible. We consider that from a detailed analysis of LTPL spectra at 2 K the concentration of deep levels in ultra-pure GaAs can be determined.
OPTICAL AND TRANSPORT PROPERTIES OF p-TYPE GaAs
ABSTRACT Electrical properties such as electrical resistivity, Hall coefficient, Hall mobility, carrier concentration of p-type GaAs samples were studied at room temperature (300 K). Resistivity was found to be of the order of 5.6 × 10-3Ω-cm. The Hall coefficient (RH) was calculated to be 7.69 × 10-1cm3/C and Hall mobility (μH) was found to be 131cm2/V-s at room temperature from Hall effect measurements. Carrier concentration was estimated to be 8.12 × 1018/cm3 and the Fermi level was calculated directly from carrier density data which was 0.33 eV. Photoconductivity measurements were carried on by varying sample current, light intensity and temperature at constant chopping frequency 45.60 Hz in all the cases mentioned above. It was observed that within the range of sample current 0.1 - 0.25mA photoconductivity remains almost constant at room temperature 300K and it was found to be varying non-linearly with light intensity within the range 37 - 12780 lux. Photoconductivity was observed to be increasing linearly with temperature between 308 and 428 K. Absorption coefficient (α) of the samples has been studied with variation of wavelength (300 -2500 nm). The value of optical band gap energy was calculated between 1.34 and 1.41eV for the material from the graph of (αhν) 2 plotted against photon energy. The value of lattice parameter (a) was found to be 5.651Å by implying X-ray diffraction method (XRD).
Near Bandedge Optical Absorption Processes in Semi Insulating and N-Type GaAs
2002
Near bandedge optical absorption processes in semi-insulating (SI) GaAs and Te-doped n-type GaAs crystals were investigated in the temperature range 10--300 K. We observed absorption peaks whose maximum energies Em, ranging from 1.498 to 1.485 eV decrease as the temperature increases from 10 K to 100 K. The peaks for both SI and n-type GaAs disappeared above 100 K. Extrapolating the graphs of Eg-Em versus temperature, we observed that near bandedge absorption is overlapped by the conduction band at about 220 K and 260 K for n-type and SI samples, respectively. Furthermore, we demonstrated that the absorption in the region of near bandedge can be photo-quenched using further irradiation after EL2 photo-quenching at higher temperatures. Comparison of the absorption measurements with the spectral photo-current measurements, we conclude that Reverse Contrast (RC) centres that cause such absorption at energies close to the bandedge have no intra-centre transition.
The electric field effects on intersubband optical absorption of Si δ-doped GaAs layer
Solid State Communications, 2003
The intersubband transitions in Si d-doped GaAs structures is theoretically investigated for different applied electric fields. For an uniform distribution the electronic structure has been calculated by solving the Schrödinger and Poisson equations selfconsistently. From our calculations, it is found that the subband energies and intersubband optical absorption is quite sensitive to the applied electric field. This gives a new degree of freedom in various device applications based on the intersubband transitions of electrons.
Infrared techniques for semiconductor characterization
Infrared Physics, 1970
The advantages and limitations of optical measurements are discussed and compared with electrical and galvano-magnetic measurements as a routine means of examining the electronic properties of semiconductors. Rapid, accurate, non-destructive optical methods for determining the free charge carrier concentration (N) and mobility (p) in n-type GaAs are described. Measurements of both transmission and reflection over the wavelength range 5-35 pm are shown to be useful for determining N and p in crystals which contain from 5 x 1Ol7 to about 1 x 10ly carriers/cm 3. For carrier concentrations from 5 x 1016/cm3 to 5 x 1018/cm3 transmission measurements from 5 to 14rm were found to be suitable. The optically determined carrier concentration and mobility of polished n-GaAs slices were, in almost all cases, within 30% of the carrier concentration and mobility calculated from Hall effect measurements. A wide variety of crystal shapes and sizes could be evaluated and, with suitable beam condensers and masks, a sampling spot diameter of 1.5 mm was obtained; with the addition of a simple mechanical sample scanning apparatus, inhomogeneity in dopant distribution was easily detected.