Crystalline InP Research Articles

X-Ray Photoelectron Study of Yb-Doped InP

X-ray photoelectron spectra of core levels are reported for InP:Yb. Crystalline InP, doped with Yb to a level of 0.5 at.%, was grown by the synthesized solute diffusion method. An analysis of the core-level spectra of the constituent components, i.e. In 3d512 and P 2p, revealed a minor influence of the surface oxide species, mainly in the phosphate-like form. The spectrum of the Yb 4d core level was also recorded. The energy of the Yb 4d312 peak was found identical to that in Yb metal, whereas the 4d512 peak was found to be shifted to higher binding energies. This effect was found comparable to the case of advanced oxidation of Yb thus confirming its high reactivity, even as a bulk dopant. The data give also a rare experimental example of detection of bulk dopant atoms in a semiconductor matrix by X-ray photoelectron spectroscopy at the limit of detectability.

InP growth on ion-implanted InP substrate: a new method to achieve selective area MOVPE

A novel method for selective area MOVPE of InP on ion-implanted InP substrate has been developed. The substrate is partially masked by photoresist, which protects the underlying surface from modification by ion implantation. On these areas the InP growth is single crystalline while a more polycrystalline phase is deposited on the implanted areas. Depending on the TMIn partial pressure, the growth rate of the single crystalline material is enhanced compared to the polycrystalline phase, which leads to selective growth at a low TMIn partial pressure and to phase selective growth at high partial pressures. The carrier mobility and the specific resistance of the polycrystalline material was found to be higher than in single crystalline InP. The ratio of the mobility in polycrystalline to the mobility in single crystalline InP depends on the growth temperature. The influence of the growth parameters, total reactor pressure, TMIn partial pressure, growth temperature and time, and the influence of the geometric dimensions was investigated. This technique should allow the growth of small structures at short distances like matrices of quantum dots or quantum wires.

In-situ monitoring of surface chemistry and charge transfer at semiconductor surfaces

A simple method for in-situ distinction between the effect of dipole formation/annihilation and charge transfer to/from surface gap states on the semiconductor work function is described. The technique is based on simultaneous monitoring of the work function and photovoltage at the semiconductor surface. The approach is illustrated by experiments performed on single crystalline InP(100) surfaces and polycrystalline Cu(In,Ga)Se 2.

Raman-scattering assessment of Si+-implantation damage in InP

We studied the lattice damage caused by Si+ implantation into semi-insulating InP, with doses in the range of 1012 to 5×1014 cm−2, and the subsequent lattice recovery achieved by rapid thermal annealing (RTA), by means of Raman spectroscopy. With increasing implantation dose, an intensity reduction of the first- and second-order Raman peaks characteristic of crystalline InP is observed, together with the enhancement of disorder-activated modes. In samples implanted with doses higher than 1014 cm−2 the Raman spectra resembles that of amorphous InP, and the samples can be considered as fully amorphized. By RTA at 875 °C for 10 s, sample crystallinity is recovered, even in the case of those samples implanted with the highest dose. After annealing, the Raman spectra show no evidence of disorder-activated modes, and the intensity of the characteristic second-order peaks approaches the value found in unimplanted InP.

A comparison of annealing kinetics in crystalline and amorphous InP

Relaxation of ion-induced strain in crystalline InP is compared with structural relaxation of amorphous InP. Crystalline InP was bombarded with Se ions at low fluence to produce a damaged surface layer. The room temperature evolution of strain in this layer was determined by high-resolution x-ray diffraction and compared to the evolution of the defect-activated viscosity of amorphous InP during similar room temperature structural relaxation. Both processes can be described by double exponential decay functions with characteristic times of a few hours to a few days.

Persistent room-temperature relaxation of InP amorphized and compacted by MeV ion beams

Ion beam induced deformation and compaction has been observed in InP, amorphized by MeV Se ion implantation. The initial density of amorphous InP is 0.55%±0.05% larger than that of crystalline InP. During a period of two months, most of the excess density is lost in a spontaneous, room-temperature relaxation. This relaxation can be described by two time constants: τ1≊8±2 h and τ2≊14±1 days.

Sub-gap optical properties of amorphous InP produced by ion implantation

Abstract Amorphous InP layers were produced by ion implantation into semi-insulating crystalline InP. The absorption coefficient and the refractive index of this amorphous InP were determined in the frequency range 0.2 eV h ω eV . The refractive index is increased by 20% with respect to the unimplanted substrate. The sub-gap absorption coefficient yields an optical gap of about 0.65 eV. The comparison of the spectral dependence of the absorption coefficient of ion implanted amorphous InP with that of flash evaporated amorphous InP indicates a higher degree of disorder in the implanted than in the evaporated material.

Electronic structure of crystalline InP oxides

Tight-binding electronic structure calculations for all crystalline InP oxides are presented. X-ray-photoemission valence band spectra are compared with these results and the different contributions to each spectrum are analyzed. A systematic correlation with the local atomic order is found. The notion of oxidation number is analyzed in terms of the electronic structure, concluding that whatever the coordination for a given atom is, the oxidation number is the same.

S-passivated InP (100)-(1×1) surface prepared by a wet chemical process

A highly stable crystalline S-passivated InP(100) surface has been obtained by a simple wet chemical process, using illumination and heated (NH4)2S solution. Low-energy electron diffraction studies show a (1×1) diffraction pattern, which persists even after 3 days of exposure to the atmosphere. High-resolution photoemission studies show that the surface is terminated with a monolayer of sulfur, which forms bridge bonds only to indium. The P 2p core level is identical to that of a vacuum-cleaved InP surface. A possible structural model is presented.

Direct infrared and visible absorption spectroscopy of stoichiometric and nonstoichiometric clusters of indium phosphide

Resonant two-color and one-color photodissociation spectroscopy is performed on neutral InxPy clusters with x+y=5 to 14 atoms. Absorption spectra of 29 different InxPy clusters are obtained for excitation energies between 0.84 and 1.84 eV. The absorption behavior is qualitatively similar for all of these clusters. An optical-gap-like absorption feature is observed at the blue end of the spectra, particularly for clusters which contain an even number of atoms. This feature shifts as a function of cluster size, but has an onset close to the band gap of bulk crystalline InP. Weaker absorptions are observed tailing to the red. A distinct absorption peak is also observed near the bulk InP band band gap for odd-numbered clusters with a stoichiometry of Inx+3Px. An empirical fitting of the low energy absorption tails reveals a correlation between the optical behaviors of these tiny clusters and amorphous semiconductors.

Composition and structure of ion‐bombardment‐induced growth cones on InP

AbstractThe previously reported1,2 effect of low‐energy (several keV) ion bombardment on the surface topography of InP was investigated by scanning transmission electron microscopy. Convergent beam electron diffraction patterns of the surface growth ‘cones’ induced by argon ion bombardment of (100) InP between 7 and 10 keV proved the cones to consist of crystalline InP (and not metallic indium, as has sometimes been claimed). The investigation showed that the irradiated surface region is not rendered completely amorphous but that it recrystallizes from the crystalline/amorphous interface in a columnar growth pattern, often terminating in growth cones protruding above the surface. Weak beam investigations revealed that the overwhelming majority of the cones have the orientation of the substrate. These phenomena were observed at all dose densities from 7 × 1015 to 2 × 1017 cm−2.

Defect activated infrared multiphonon excitation in iron-doped semi-insulating indium phosphide

Multiphonon excitation induced by long-range order crystal-field and short-range order Jahn–Teller distortion effects is observed in Fe-doped semi-insulating InP in the spectral range from 400 to 1100 cm−1 for infrared light propagating in a slab waveguide geometry. Transmission measurement data are analyzed in terms of phonon energies at critical points in the Brillouin zone. The phonon energies obtained are in excellent agreement with recently reported second order Raman scattering spectra and two-phonon absorption measurements of crystalline InP. The energy differences between the nearly degenerate two phonon transverse optical+longitudinal optical transitions at the Γ, X, and L points are also resolved and shown to be 10 cm−1. No localized mode or vibronic level absorption is observed, consistent with the relatively low concentration of Fe impurities in the samples.

Near-ir absorption in neutral clusters of indium phosphide: Observation of an optical-gaplike feature at 1.3-1.5 eV.

Near-ir absorption spectra are obtained for neutral InP clusters in the range 1.0--1.6 eV using two-color resonant two-photon dissociation spectroscopy. All stoichiometric and many off-stoichiometric InP clusters exhibit a distinct continuum absorption with an onset of 1.3--1.5 eV, close to the band gap of crystalline InP. Additional weaker absorptions are also seen at lower energies. An explanation is given for why these spectra are so similar to those of III-V semiconductor solids.

Influence of the structure of InP thin films on electron energy loss spectra

AbstractElectron energy loss measurements were carried out on single crystalline, polycrystalline, and amorphous InP thin films. Plasmon data and structures of − Im ε−1 are discussed in dependence on degree of crystallinity.

Properties of in and p subcascades in a crystalline ion-implanted InP target

Abstract Results of a Monte Carlo simulation of the damage formation in a crystalline InP target are reported. The simulation analyses the features of the two recoil populations for different orientations of the target.

Raman investigation of the InP lattice dynamics

The second-order Raman spectra of crystalline InP have been investigated at 77 and 300K and the decomposition into the Gamma 1, Gamma 12 and Gamma 15 components performed between 10 and 700 cm-1. Several determinations of the one-phonon density of states in InP are deduced from the second-order scattering of crystalline samples or from the first-order scattering of mechanically perturbed and ion-implanted samples.

K-Edge XANES of GaP, InP and GaSb

X-ray-absorption near-edge structure (XANES) spectra for crystalline GaP, InP and GaSb were measured for each Ga and P K-edge region. Full multiple scattering calculations are performed. The information on the charge distribution around the X-ray-absorbing atom can be obtained by comparing the experimental XANES spectra with the full multiple scattering calculations. The effective cation charge distributions are predicted to be q= ∼0.33 for GaP, q=0.42 ∼0.5 for InP and q \\lesssim0.26 for GaSb.

Vibrational properties of proton-implanted crystalline InP

Infrared transmission spectra of proton implanted crystalline InP exhibit local vibrational modes at 2197 and 2212 cm -1 which are ascribed to P—H bond vibrations. The dependence of the integrated absorption A of the bands due to the P—H bonds in proton-implanted InP and GaP on the proton dose D follows the relation A ∼ D n with n ≈ 0.4. For GaP it is established that A is proportional to the mean damage density.

Band-structure calculations of the two-photon absorption coefficients of GaAs, InP, CdTe, and ZnSe

The two-photon absorption coefficients of crystalline GaAs, InP, CdTe, and ZnSe at 1.064 and 0.694 \ensuremath{\mu}m are calculated by means of a new model which combines the elements of second-order perturbation theory and band-structure calculations. A sufficient number of intermediate states are included to ensure adequate convergence. This calculational procedure is shown to represent a significant improvement over currently available theoretical models, and the results are in good agreement with available experimental data.

The luminescence of defects introduced by mechanical damage of InP

When crystalline InP is subjected to mechanical damage by scratching or cleaving in vacuum, a new luminescence transition near 1.3 eV results. The spectrum consists of a doublet split by ∼5 meV. Thermal quenching occurs above 100 K with an activation energy of 120 meV. Annealing to 300 K in the dark removes the luminescence centers, and the annealing temperature is reduced to about 200 K with illumination. We interpret the luminescence centers as native defects acting as electron traps of depth ∼100 meV. The defects are believed to be introduced by the process of plastic deformation of the crystal.