Photoconduction spectroscopy of p-type GaSb films (original) (raw)
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Raman Spectroscopy for The Description of Surface Electrical Properties of p-type GaSb Thin Films
The effect of doping level at room temperature on the low injection level photo-response of various un-doped and zinc doped p-type GaSb thin films were investigated using Raman spectroscopy measurements. The presence of a near-surface depletion region was determined through the comparison of the longitudinal optical (LO) phonon mode scattering and the phonon-hole Plasmon (L¯) coupled mode in samples of different doping concentrations. Taking into account the values of the carrier densities obtained using the Hall measurements and the ratios of the pick intensities of the LO and the L¯ modes, some of the near-surface characteristics, such as the band bending and the surface Fermi-level position above the valence band maximum (VBM) could be inferred as function of the doping level.
An electrochemical route to GaSb thin films
Journal of Applied Electrochemistry, 1990
An electrochemical method for the preparation of GaSb polycrystalline thin films is presented involving sequential deposition of Sb and Ga films (from an acid SbC13 solution and an alkaline GaC13 solution respectively) and a mild thermal annealing. The annealed deposits were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis (EDAX) and secondary ion mass spectrometry. An alternative approach based on the simultaneous deposition of Sb and Ga was unsuccessful.
Optical properties of GaSb(001)-c(2 × 6): The role of surface antisite defects
Physica Status Solidi B-basic Solid State Physics, 2010
We consider the formation of surface antisite defects on a previously proposed model for the GaSb(001)-c(2 × 6) surface. Based on ab initio total energy calculations, we show how these defects stabilize the otherwise metallic surface and how their formation is driven by the excess charge associated with the Sb-rich surface conditions. The surface-sensitive optical technique of reflectance anisotropy spectroscopy is shown to be crucial for detecting the defects, and computation of spectra yields a good agreement with experiment when defects are included in the surface reconstruction.
Structural evolution and characterization of heteroepitaxial GaSb thin films on Si (111) substrates
We synthesized barium titanate (BaTiOr) particles by heat-treating the polymeric precursors in air at 500-900°C and proposed a model for the BaTiO) formation from the polymeric precursors. The model contained a series of steps such as the transformation of the precursor to amorphous barium titanate, three-dimensional nucleation and growth, and solid-state reaction. We investigated the crystal structure of the particles (20 nm in size.), processed at 600°C. using X-ray powder diffractometry (XRD) and Raman spectroscopy. The XRD measurement indicated formation of cubic BaTiOr, and the Raman spectrum indicated that the particles of 20 nm size might have had a tetragonrd symmetry. For the particles heated at 5OO"C, XRD and Raman spectroscopy data suggested the presence of a high-temperature hexagonal phase at room temperature. High-resolution transmission electron microscopy indicated that the peaks that were ascribed to the above phase, in the Raman and XRD spectra, may originate from (111) planar defects in the particles. 0
Photothermal investigations of doping effects on opto-thermal properties of bulk GaSb
Journal of Alloys and Compounds, 2009
GaSb is a direct gap semiconductor (0.72 ev) having good carriers motility and significant electro-optical potential in the near IR range. As substrate or active layer, GaSb can be employed in conjunction with many semiconductors such as (AlGa)Sb or In(AsSb) and has interesting hetero junction potential for detectors, lasers and quantum well structures. The aim of this work is to investigate the influence of doping on the opto-thermal properties (optical absorption, refractive index and thermal diffusivity) of doped and undoped GaSb bulk throw, the phothermal deflection and spectroscopic reflectivity. It is found that absorption below the gap and thermal diffusivity increases with doping concentration.
Influence of Substrate Preparation on the Morphology of GaSb Films Grown by Molecular Beam Epitaxy
Journal of The Electrochemical Society, 1985
The chemical etching of (100)-oriented GaSb substrate by several different treatments has been studied. The morphology of the MBE-grown GaSb films strongly depends on the substrate preparation prior to epitaxial growth. It is shown that some defects which originate at the substrate propagate to the surface of the films, in case of the improper chemical treatment, and degrade the morphology of the films. The excellent surface morphology of the film could be obtained reproducibly by treating the substrate with CH~COOH-HNO3-HF and subsequent HNO3-HC1 solutions.
Optical investigation of GaSb thin films grown on GaAs by metalorganic magnetron sputtering
Thin Solid Films, 2008
Metalorganic magnetron sputtering (MOMS) technology has been applied to the growth of epitaxial GaSb layers on GaAs (001). Optical studies are performed on a series of GaSb/GaAs samples grown under different growth conditions. Raman scattering measurements indicated the improvement of the crystalline quality of the GaSb thin film from the interface toward the surface with decreasing substrate growth temperature from 480°C to 400°C. Fourier transform infrared (FTIR) reflectance revealed the possible existence of an intermixed GaSb-GaAs layer near the interface. In UV reflectance spectra, the shapes of the high energy transition bands were found to be associated with the GaSb film quality.
Fundamental characterization studies of GaSb solar cells
1991
Measured forward and reverse current versus voltage curves for GaSb cells at various temperatures and for different substrate dopant densities are modeled. The authors show that tunneling across a lower bandgap for reverse-biased GaSb cells allows nondestructive reverse current flow at low voltages. Thus, the GaSb IR cell doubles as a bypass diode, providing shading protection for the GaAs cell. Measured GaSb quantum yield curves are also modeled, and the resultant minority carrier diffusion lengths are compared with electron beam induced current measurements. It is found that the GaSb cell properties are consistent with predictions based on a direct gap single-crystal material
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1990
GaSb (00l) surfaces were prepared by molecular-beam epitaxy. Auger electron spectroscopy (AES) and electron energy-loss spectroscopy (EELS) are reported for clean surfaces exposed to oxygen, and during the process the ionization gauge of the vacuum system is turned on. Successive stages of chemisorption can be distinguished. For oxygen coverage up to 0.5 monolayer, the surface states are saturated by bonding of the oxygen with Ga and Sb atoms. Sb atoms desorb caus~ng signi~cant Sb depletion in the first layer. Larger exposures further increase the coverage and mduce, m the EELS spectra, losses related to 0(2p) and 0(2s) atomic states and new plasmon excitations. In the AES spectra the shift of Auger emission lines which are characteristic of Sb and Ga oxide forms appear; at coverages of about one monolayer back bonds break forming Sb 2 0 3 and Ga 2 0 3 , Further exposures to oxygen result in thicker oxide layers of Ga and Sb.