Infrared response of multiple-component free-carrier plasma in heavily doped p-type GaAs (original) (raw)

GaAs peculiarities related with inhomogeneities and the methods for reveal of their properties

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2001

The inhomogeneities in as-grown and irradiated GaAs crystals and structures, their properties and role have been analysed. The influence of inhomogeneities on the properties of crystal and Schottky diode structure are presented. The possibilities of different methods for material and structure characterisation (Hall effect and magnetoresistance, noise spectra, thermally stimulated current and polarisation, photoconductivity kinetics and spectrum, light-induced diffraction) are discussed.

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.

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 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).

Electrical Properties of Heavily Be-doped GaAs grown by Molecular Beam Epitaxy

MRS Proceedings, 1989

Electrical properties of heavily Be-doped GaAs grown by molecular beam epitaxy were investigated systematically in a wide range of Be-concentration from lX 1014 up to 2X 1020 cm-3 by using yan der Pauw technique. Probable carrier scattering mechanisms observed in this work are discussed by taking into account the radiative mechanisms of several new photoluminescence emissions previously observed in the band-edge-emission region of the samples. All samples were checked their electrical properties first at roomtemperature. Five selected samples out of them were measured from 10* K up to room-temperature. Samples having the carrier concentration from 1014 to 1018 cm-3 presented typical semiconductor-like conduction with finite carrier excitation energy. For samples having carrier concentration 7X 1016 cm-3, the conduction mechanism at high temperature region above 30* K was dominated by holes thermally excited into valence band. At low temperature region below 300 K , it was dominated by holes hopping from neutral to ionized acceptors with the assistance of phonons. Hole mobilities of samples having the carrier concentration from 1017 to 1018 cm-3 showed an anomalous behavior in the low temperature region, which suggests the presence of a new type of carrier scattering mechanism. A radiative center denoted by [g-gj observed ii this concentration region will be a candidate scattering center to explain these electrical behaviors. Samples having the carrier concentration larger than 1019 cm-3 demonstrated typically metallic electric conduction not owing to thermally excited carriers, which means that an impurity band is formed but merged with valence band. The density of state of this combined valence band mixed with impurity band can be supposed to reflect carrier concentration dependence of the PL emission bands observed in this region, i.e. [g-gla , [g-gL] and [g-g]y

Interface properties of isotype GaAs/(In,Ga)P/GaAs heterojunctions grown by metalorganic-vapour-phase epitaxy on GaAs

Journal of Crystal Growth, 2000

Metal-semiconductor contacts are used to examine the depth-resolved electrical characteristics of Si-and Zn-doped GaAs/(In,Ga)P/GaAs heterojunctions by capacitance}voltage measurements and deep-level transient Fourier spectroscopy. The experimental depth pro"les of the carrier concentration are compared with calculations based on selfconsistent solutions of the Poisson equation. By varying the growth conditions, heterointerfaces of GaAs with disordered or double-and single-variant ordered (In,Ga)P layers are produced. It is shown that normal [(In,Ga)P-on-GaAs] and inverted [GaAs-on-(In,Ga)P] interfaces are not equivalent with respect to their electrical properties. For the inverted Si-doped heterointerface, the depth pro"les of the electron concentration strongly depend on the growth conditions. In spite of a large carrier de"cit at this interface, the density of interfacial traps in the upper half of the bandgap is found to be low in the 10 cm\ range. For interfaces with disordered (In,Ga)P, the conduction and valence band o!sets are independently determined to be 0.20 and 0.27 eV, respectively. These heterointerfaces exhibit type-I character, in agreement with theoretical predictions. For interfaces with single-variant ordered (In,Ga)P, the conduction band discontinuity is found to be also 0.20 eV, in contrast to calculations of the band alignment for ordered (In,Ga)P, which predict !0.13 eV.

Two-dimensional versus three-dimensional behavior of a free-carrier gas in δ-dopedp-type GaAs(001)

Physical Review B, 1994

The free-carrier-induced plasma excitation in 5-doped p-type GaAs(001) has been studied by means of high-resolution electron-energy-loss spectroscopy (HREELS). Several samples, with different values of doping and depth of the dopant layer, have been investigated at various primary-beam energies. The HREEL spectra show a strong dependence on the doping level. We were able to reproduce satisfactorily all the measured spectra using a suitable dielectric model of a classically con6ned free-carrier gas, pointing out the two-dimensional character of the free-carrier gas in the samples having the two lowest dopings. On the contrary, a characteristic three-dimensional behavior of the plasma excitation is exhibited by the most doped sample.