B. H. Bairamov

Determination of the hole concentration and mobility of p-GaP by Hall and by Raman measurements

Larger hole concentrations and lower mobilities are measured by Raman scattering of p-GaP in comparison with results of Hall and conductivity investigations. The Hall factor which is responsible for the differences can be obtained by these measurements and is discussed on the basis of a two-band model.

Observation of raman scattering by localized optical phonons bound to neutral donors in GaP:Si

Abstract Raman scattering by localized optical phonons bound to neutral donors with degenerate ground state has been observed in GaP:Si. The scattering efficiency was measured at T=6.0±0.1 K as a function of the net donor concentration ND-NA ranging from 1.6 ·1017 to 7.1· 1017 cm-3. It is found that reasonable agreement with the theory of weakly coupled electron-phonon modes obtained if a Bohr radius of a 0 =5.4 A is used, whereas a 0 =7.5 A is obtained in the hydrogenic effective-mass approximation using the ionization energy ED=86.7 meV.

Quasielastic Raman scattering in n-type GaAs

The quasielastic part of the Raman spectrum in the spectral range nu <100 cm-1 offers the possibility of detecting the free electron concentration of semiconductors down to about 5*1014 cm-3. A series of n-type GaAs samples was investigated using NIR Raman spectroscopy ( lambda ex=1064 nm), and an analytical method to obtain the carrier concentrations from the spectra is proposed. The sources of error and the limits of the method are discussed by comparison with the corresponding Hall measurements. Within the range 1*1015 cm-3<n<1*1017 cm-3 the accuracy of the obtained free electron concentrations is estimated to be about 25%. The detection limit of the quasielastic Raman spectroscopy is nearly two orders of magnitude better than the determination of n from the coupled LO-phonon-plasmon modes.

Identification of impurities in GaP by Raman spectroscopy

Abstract Neutral donors in polar semiconductors give rise to resonances between dipole active electronic transitions and LO-phonons. Localized at neutral donors mixed modes then can be excited and detected by Raman spectroscopy, the energy of which depend on the chemical nature of the impurities. It is demonstrated on GaP:S, Te, Si and Sn that these resonances can be used for an impurity identification in the concentration range ≳ 10 17 cm −3 .

Near infrared inelastic light scattering spectroscopy of high efficiency solar cells device structures based on III-V compounds

The authors report on the experimental and theoretical study of the near infrared inelastic electronic light scattering of the most promising high-efficiency tandem concentrator solar cells device structures based on nand p-type GaAs, InP, InGaAs, and InGaAsP, grown by LPE. They show that the scattering mechanisms associated with charge-, spin-, and momentum-density fluctuations of free electron gas are represented by different line shapes and occurred in corresponding concentration ranges. A new approach to the problem and observed results provide clear evidence that the sensitivity of the developed measurements in solar cell semiconductor structures provide a unique opportunity for their characterization and optimization.

Inelastic light scattering characterization of epitaxial grown III–V semiconductor microstructures

Abstract Quasi-elastic light scattering by electron single particle excitations and inelastic light scattering by coupled electron-phonon excitations are studied in epitaxial layers grown on semiinsulating AIII-BV-substrates. A Nd:YAG laser beam was used as a microscope. The spectra reflect the concentration and distribution of the free carriers. In the range of low electron concentrations the scattering by electron density fluctuations dominates which is accurately described by Gaussian curves at room temperature.