Electrical and optical properties of gallium phosphide films

The electrical and optical properties of gallium phosphide films, prepared by the explosive evaporation and three-temperature methods, are studied. It is shown that film properties are strongly dependent on method of preparation and substrate temperature. Gallium phosphide films prepared by explosive evaporation having perfect structure possess the best electrical and optical properties.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 6, pp. 54–58, June, 1971.     

Many-quantum absorption in gallium phosphide

A study has been made of photoconductivity in GaP induced by 1.78 and 1.17 eV photons from Q-switched ruby or neodymium lasers. Many-quantum processes were observed with 2 to 7 photons participating simultaneously. Double-photon absorption with a phonon participating has also been investigated. The observed many-quantum transitions confirm the recent ideas about GaP zone structure.Based on a generating function method, the theory of many-quantum transitions is developed which takes into account the peculiarities of crystal zone structure. The experimental data are in satisfactory agreement with the theory.Both the many-quantum theory and the experimental method reported in the present paper permit one to study the zone structure of various crystals and to obtain new or supplementary information on fundamental optical constants of solids.     

Ellipsometric analysis and optical absorption characterization of gallium phosphide nanoparticulate thin film

Gallium phosphide (GaP) nanoparticulate thin films were easily fabricated by colloidal suspension deposition via GaP nanoparticles dispersed in N,N-dimethylformamide. The microstructure of the film was performed by x-ray diffraction, high resolution transmission electron microscopy and field emission scanning electron microscopy. The film was further investigated by spectroscopic ellipsometry. After the model GaP+void|SiO₂ was built and an effective medium approximation was adopted, the values of the refractive index n and the extinction coefficient k were calculated for the energy range of 0.75 eV-4.0 eV using the dispersion formula in DeltaPsi2 software. The absorption coefficient of the film was calculated from its k and its energy gaps were further estimated according to the Tauc equation, which were further verified by its fluorescence spectrum measurement. The structure and optical absorption properties of the nanoparticulate films are promising for their potential applications in hybrid solar cells.     

Raman scattering from surface optical phonon mode in gallium phosphide nanomaterials

The Raman scattering from gallium phosphide (GaP) nanoparticles (~53 nm) and nanosolids has been investigated. By means of Lorentzian fitting of the Raman scattering spectra, a surface optical phonon (SO) peak located between the transverse optical (TO) phonon and longitudinal optical (LO) phonon frequencies became observable. It has been proved by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) that a core-shell heterostructure is characteristic of the structure of GaP nanoparticles. According to electromagnetic theory, the SO frequency of the piezoelectric/semiconductor heterostructural nanomaterials was calculated.     

Surface states on gallium phosphide

Ultraviolet photoelectron spectroscopy shows that the surface Fermi level of clean cleaved GaP (10) is pinned 1.50 eV above the valence band maximum of empty surface states. Synchrotron radiation-excited photo-emission partial yield spectroscopy supports this conclusion.     

The optical properties of Be,Mg and Zn-diffused gallium phosphide

Interest in the Ga-site acceptors Be and Mg was stimulated by the possibility that they might produce efficient luminescence on association with O, analogous to the well-known red Zn-O luminescence in GaP but at higher transition energy. Attention was directed to diffusion doping by Be and Mg of GaP O-doped during growth because the reactivity of Be and Mg with O renders double doping during crystal growth very difficult. Structured green donor-acceptor pair spectra were observed at 1.6°K from many Be-diffused crystals, yielding an accurate measure of (E_A)_BE, 50 ± 1 meV. Moderately efficient orange-red luminescence was also observed below ∼ 100 °K from these crystals, but the intensity of this luminescence decreased rapidly to negligible levels by ∼ 200°K. This luminescence also contains sharp structure at 1.6°K, of a form characteristic of the decay of excitons bound to complex centres. Many sharp phonon replicas occur, involving local modes as well as characteristic GaP modes. One set of no-phonon lines, at least, near 2.19 eV, shows zero-field splitting, luminescence decay times and behaviour in magnetic and external strain fields characteristic of exciton decay at a centre with <100>; or <111>-type symmetry axes, containing no extra electronic particles. The exciton state is split by 2.4 meV by J-J coupling, and the axial field of the centre splits the hole states by ∼ 1.0 meV. These bound excitons are specifically characteristics of diffused GaP and appear analogous to bound excitons observed below 2.12 eV in Zn-diffused GaP. It is probable that the relevant centres contain diffusion components such as Be or Zn interstitials and improbable that O_P is involved. By contrast, weak orange bound exciton luminescence observed in Mg-diffused GaP does involve O, presumably as O_P. No analysis of the magneto-optical behaviour of this Mg-related bound exciton was possible in our crystals, so its symmetry axis was not established. It is possible that this is the Mg_Ga-O_P bound exciton. If so, the two-fold reductions in the exciton localisation energy from ∼ 0.32 eV to ∼ 0.15 eV and in the mass of the Ga-site substituent has produced dramatic changes in the form of the phonon cooperation between the Zn-O and “Mg-O” excitons. The “Mg-O” exciton luminescence is not dominant in our crystals, even at low temperature. The exciton state is again split by a local crystal field as well as by J-J coupling, but here the former splitting is predominant; 2_∈0 = 3.9 meV, Δ = 0.60 meV.     

Forbidden band width and optical properties of thin gallium phosphide films

The temperature dependence of the forbidden band width of gallium phosphide films deposited by a discrete method on various substrates has been investigated in the present work. The influence of the material and temperature of the substrate on the forbidden band width and its change with thickness, are determined. This latter is treated as the appearance of a quantum dimensional effect. The dispersion of gallium phosphide films is measured in the visible band of the spectrum.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 9, pp. 88–92, September, 1971.     

The structural and optical properties of gallium arsenic nanoparticles

Spherical gallium arsenic nanoparticles prepared by thermal evaporation method have been fabricated successfully. The structural and optical properties of GaAs nanoparticles are studied in detail. It is found that while the growth pressure rises from 0.4 to 5 Torr, the average size of GaAs nanoparticles increases from 6 to 12 nm and standard deviation keeps almost the same (2 nm) except for 0.5 Torr. By using transmission electron microscopy and Raman spectra, a critical preparation condition has been found which characterize the amorphous to crystal transition of GaAs nanoparticles.     

Impurity absorption in gallium phosphide doped with zinc and oxygen

The extrinsic optical properties were investigated in homogeneous GaP crystals at room temperature. The transmission of extrinsic light is influenced by a simultaneous illumination of an additional light of different frequency. This light changes the occupancy of an impurity level. A simple theory is given, which relates this change in transmission of the extrinsic light to the optical cross sections of the impurity level. We had to use steady light because of the large relaxation time, but still obtained a resolution of 2 × 10⁻⁵ in the relative transmission change. The spectral dependence of the optical cross sections for an impurity level 0·9 eV below the conduction band were calculated. Another level approximately 1·85 eV from a band edge was also seen in these measurements, but it had complex optical properties. Both levels were seen in a direct measurement of the absorption coefficient.     

Electrical and luminescent properties of gallium phosphide with radiation defects

The energy spectrum of local levels and the effect of radiation damage on intensity and character of cathode luminescence lines in the visible region of the spectrum in gallium phosphide single crystals prepared from a solution-melt by the Chochralski method are examined. It is shown that as a result of irradiation by fast electrons with E_e=1 Mev and Co 60 -quanta, both donor and acceptor centers are introduced into the original crystals. New radiation centers producing lines in the spectral range studied (500–600 nm) were not observed after irradiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 49–54, June, 1976.     

Forbidden optical transitions between impurity levels in silicon and gallium phosphide

Experimental estimates are made of absorption cross sections for forbidden optical transitions from the ground state to long-lived excited states of P, As, Sb, In, and Ga impurities in silicon and Te impurities in gallium phosphide. The results can be used to predict the possibility of long-wavelength stimulated emission being excited as a result of the population inversion of long-lived impurity states in these materials.     

Direct observation of the lifetime of a polariton mode in gallium phosphide

A polariton mode not far from the fundamental TO frequency in GaP is excited using the stimulated Raman effect. The degree of lattice excitation is directly observed as a function of time by a picosecond probe pulse. A relaxation time of 5.5 psec was measured in agreement with infrared data.     

有序金纳米颗粒阵列的制备及光吸收特性研究

采用纳米球刻蚀技术中漂移法在玻璃基片上制备较大 面积不同直径的聚苯乙烯小球掩模板, 采用磁控溅射技术在掩模板上沉积不同厚度的金薄膜, 去除聚苯乙烯小球后, 通过扫描电子显微镜观察到周期排列的三角状金纳米颗粒点阵. 通过紫外-可见分光光度计测试所制备样品的光吸收特性, 发现表面等离子体共振峰随粒径增大发生红移, 随金纳米颗粒高度增加发生蓝移. 基于Mie理论, 利用Matlab软件编程对不同粒径的金阵列光吸收特性进行理论模拟, 并与实验结果进行对比. 关键词： 纳米球刻蚀 金纳米颗粒阵列 表面等离子体共振     

Infrared absorption by zone edge lattice vibrations in mixed gallium indium phosphide

The combinations of zone edge phonons of mixed Ga_1?xIn_xP have been studied by means of infrared absorption, these crystals exhibit a one mode behavior for both the zone center and the zone edge phonons.     

Heat treatment of gallium phosphide

Annealing effect of GaP depends on the phosphorus pressure observed by Hall effect, X-ray diffraction and photoluminescence. The phosphorus pressure for the peaks of the lattice constant after annealing coincide with that for the high resistivity in the Hall measurement.     

Anomalous polarization dependence of the photon drag and optical rectification fields inn-type gallium phosphide

The photon drag and optical rectification response fromn-type gallium phosphide containing 2.4×10¹⁶ electrons cm^–3 has been studied using laser sources at 10.61 and 2.83m. By using different contact configurations, the existence of an additional electric field term in the propagation direction has been deduced. This field is shown to arise from the spatial derivatives of the photon drag and optical rectification field components caused by absorption of the radiation. The importance of this effect in detector design is considered.     

Surface and interface effects in the optical properties of silver nanoparticles

We present novel experimental results about influences of surrounding foreign materials on optical properties of small silver clusters. First we show spectra of free cluster beams produced with different seeding gases Ar, Kr, Xe. Second, we estimate, from measured spectra, the cluster deformations and contact areas after deposition on different substrates (Cr₂O₃ and MgF₂) at room temperature and on SiO₂ at 110 K and between 160 K and 300 K. Third, we present and compare the static and dynamic charge transfer after embedding the clusters in various fluorides and compare with previous results on oxides. Received 2 September 1998 and Received in final form 3 January 1999