InP Melt Research Articles

Rapid in-situ phosphorus injection synthesis of large quantity InP polycrystalline

In this paper, a large quantity rapid in-suit phosphorus injection synthesis technology of InP polycrystalline is presented. 20 Kg high-purity InP melt has been synthesized in 170 min, which is the fastest and largest synthesis of InP polycrystalline reported so far. Melt temperature and phosphorus injection rate are two key parameters affecting the synthesis result. Synthesis experiments were carried out under various melt temperatures, the optimal synthesis temperatures of two synthesis processes were determined. The phosphorus injection rate was controlled by adjusting the injector heating power. The injector heating power curves were optimized through experiments. The synthesized InP polycrystalline were characterized by Hall effect measurement and glow discharge mass spectrometer. The results show that the carrier concentration and mobility of synthesized 20 Kg stoichiometric InP polycrystalline were <2.0E15 cm−3 and> 4600 cm2 V−1 s−1, respectively. The results also show that high melt temperature, increase of synthesis time and deviation from stoichiometry will increase the concentration of impurities and reduce the purity of synthesized polycrystalline. It was found that synthesis rate increases with synthesis quantity. With the increase of synthesis quantity, the carrier mobility of polycrystalline increases, the carrier concentration decreases, and the polycrystalline quality can be improved.

Thermodynamics and kinetics of in situ synthesized In-P melt by the phosphorus injection and its solidification behavior

In the study, the thermodynamics and kinetics of phosphorus injected into indium melt has been investigated. The partial pressures of the phosphorus gases, P(g), P2(g) and P4(g), in equilibrium with the In-P melt with different concentrations is calculated from 1345 to 1700 K. Based on the thermodynamic analysis, the kinetic process of phosphorus injection synthesis has been studied in details, which involves the relationship among the absorption rate, synthesis efficiency, bubble diameter, rising distance of bubble, bubbling rate, injection rate, environmental pressure and melt concentration. The calculated absorption rate is in good agreement with the experimental data. Based on the kinetic analysis, 20 kg InP polycrystals are synthesized in 3 h by optimizing the synthesis parameters. It is found that local indium and phosphorus separation occurs near the bottom of the ingot during solidification from the P-rich melt. The phosphorus depositions present the radioactivity round rod, columnar polyhedron and fibrous characteristics. The formation mechanism of the separation phenomenon is analyzed. Finally, the methods of obtaining stoichiometric and P-rich polycrystals are put forward.

Anomalous increase of sub-band gap photoluminescence from InPBi layers grown by liquid phase epitaxy

The luminescence properties of InPBi layers, grown by liquid phase epitaxy from an In-P melt containing 4 and 18 wt% Bi are investigated. As-grown layers, as well as layers subjected to a high temperature anneal, are studied by atomic force microscopy (AFM), energy dispersive x rays (EDX), high resolution x ray diffraction (HRXRD) and low temperature photoluminescence (PL) spectroscopy. AFM shows formation of microscopic granular structure over the surface of the layer grown from melt containing 18 wt% Bi after a high temperature furnace anneal at 700 °C for 1 h. Lattice contraction and a decrease of Bi content is observed for both kinds of samples after anneal though it is only marginal in case of the layer grown from melt containing 4 wt% Bi but quite appreciable in case of the other sample. From EDX and XRD results, the observed decrease in Bi content as a result of high temperature anneal is suggested to be due to diffusion of Bi atoms from the layer to InP grains formed over the layer surface. 10 K PL measurements showed the expected band edge luminescence peak at 1.38 eV. A second peak at 1.33–1.34 eV is observed which shows a large post anneal enhancement for materials grown from melts containing higher amounts of Bi. It is suggested that this peak is due to luminescence from defects formed by complexes of Bi with phosphorous vacancies. Photoluminescence also revealed a broad peak between 1–1.22 eV whose intensity increased anomalously with temperature up to 104 K. The anomalous increase up to 28 K is found to be associated with a low activation energy of 0.35 meV and is speculated to be due to the transfer of holes in the localized states to the valence band. Above 28 K, PL increases with an activation energy of 9.66 meV and may be explained on the basis of similar observation made by a previous group [Chen et al Appl. Phys. Lett. 110, 051 903 (2017)] who explained the phenomenon by assuming thermal hopping of some electrons available for recombination with holes to some non-radiative states .

Investigation of vacancy defect in InP crystal by positron lifetime measurement

Positron lifetime measurements have been carried out on liquid-encapsulated Czochralski-grown undoped InP samples sliced from the middle part of ingots over the temperature range 10–300 K. And at 70 K, the spectra have been measured in darkness, under illumination of infrared LED, and with illumination off is one sample. The measurements at low temperature reveal different concentration of hydrogen indium vacancy complex V InH 4 in these samples. A relatively higher concentration of V InH 4 in samples grown from P-rich undoped InP melts can be shown. The increase of resistivity of these samples can be speculated when temperature is low enough.

Investigation of Vacancy Defect in InP Crystal by Positron Lifetime

Positron lifetime measurements were carried out on liquid-encapsulated Czochralski-grown undoped InP samples sliced from middle of ingots over the temperature range of 10 ∼ 300 K. At 70 K, the spectra were measured in darkness, under illumination of infrared LED, and while illumination off respectively on one of samples. The measurements at low temperature revealed different concentration of hydrogen indium vacancy complex V In H 4 in these samples. A relatively higher concentration of V InH 4 existing in that grown from P-rich undoped InP melts could be shown. The increase of resistivity of these samples could be speculated when temperature was low enough.

Three-dimensional numerical simulation of flow mode transition in the LEC InP melt

The flow and heat transfer of InP melt in Liquid-Encapsulated Czochralski (LEC) crystal growth has been studied using a time-dependent and three-dimensional turbulent bulk flow model. The transition from time-independent axisymmetric flow to time-dependent non-axisymmetric flow and then returning to time-independent axisymmetric flow again, is numerically observed by increasing the crystal rotation rate. The origin of the transition from an axisymmetric flow to a non-axisymmetric flow is attributed to the baroclinic instability characterised by the inclination of the temperature contours in the azimuthal direction. As a result, the critical non-dimensional parameters for the transitions were derived.

Study of indium phosphide wafers treated by long time annealing at high temperatures

High purity InP crystals were grown by liquid encapsulated Czochralski method from undoped InP melt. Wafers from the grown crystals were annealed in phosphorus ambient for 95 hours at 950 °C and cooled slowly. Conversion to semi-insulating state by annealing was studied by temperature dependent Hall measurements and low temperature optical absorption spectroscopy.

Comparative numerical study of the effects of rotating and travelling magnetic fields on the interface shape and thermal stress in the VGF growth of InP crystals

The influence of rotating magnetic fields (RMF) and travelling magnetic fields (TMF) on the growth of 2 in InP crystal by the vertical gradient freeze (VGF) method is studied by numerical simulation. Both types of magnetic field were investigated for a realistic VGF configuration with respect to the bending of the solid/liquid interface, resulting in thermoelastic stress and stability of the flow regime in the InP melt. The results of the simulations show clearly that the use of TMFs offers in contrary to RMFs a significant improvement with respect to the bending of the s/l interface as well as the resulting thermoelastic stress in the growing InP crystal.

Boron and Nitrogen in GaAs and InP Melts Equilibrated with B&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt; Flux

The boron and nitrogen contents of GaAs and InP melts equilibrated with B 2 O 3 flux were examined at 1523 and 1373 K, respectively, using a chemical equilibrium technique. GaAs or InP was melted with B 2 O 3 flux in a silica ampoule with and without a BN crucible. The boron content decreased with increasing nitrogen content in both of the melts equilibrated with B 2 O 3 flux and BN. The solubility product of BN in the melts was expressed as a function of nitrogen content. The relationship between the boron and nitrogen contents of a GaAs melt coexisted with BN agreed well with that in the residue after LEC crystal growth of GaAs. The boron content of the GaAs melt coexisted with silica was much larger than that of the GaAs melt with BN. It was suggested that the reduction of B 2 O 3 by silicon introduced into the melt from silica led the increase of boron content.

Pure and intentionally doped indium phosphide wafers treated by long time annealing at high temperatures

High-purity InP crystals were grown by the liquid encapsulated Czochralski method from undoped InP melt and from the melt doped with Ca, Zn, Fe or Mn or co-doped with Ti and Zn. Wafers from the grown crystals were annealed in phosphorus ambient for 95 h at 950 °C and cooled slowly. Conversion to the semi-insulating state by annealing was studied by temperature-dependent Hall measurements and low-temperature optical absorption spectroscopy. The undoped samples with electron concentration below 1 × 1016 cm−3 became semi-insulating due to the decreasing content of shallow donors and the increasing content of the active Fe2+ deep acceptors. The narrow absorption line of hydrogen vibrations in the complex VInH4 disappeared after annealing and three new narrow lines appeared instead. Besides, new lines appeared which were interpreted as due to Fe2+ featured by a nearby lattice defect. The n-type InP lightly doped with Zn became semi-insulating due to the formation of a new deep acceptor level at 0.33 eV below the conduction band edge.

Thermal Expansion and Some Characteristics of the Interatomic Bond Strength in Gallium and Indium Phosphides

A thermometric method is used to determine the thermal expansion coefficient of an InP melt in the temperature range of 1331–1426 K. A statistical treatment and a thermodynamic analysis of the thermal expansion coefficients for solid gallium and indium phosphides are performed using the relevant data on heat capacity. As a result, it is possible to recommend the most reliable values of the thermal expansion coefficient for these compounds in a wide temperature range. Based on these recommended data, the characteristic values of the Debye temperature and of the root-mean-square displacement of atoms from the equilibrium position are calculated, and the results are compared with the respective values obtained by other methods.

Influence of LPE growth conditions on the electroluminescence properties of InP/InGaAs(P) infrared emitting diodes

Liquid phase epitaxial growth of InP/InGaAs(P) infrared emitting diodes was studied systematically. Small area surface emitting LED chips were prepared to cover completely the 1100–1700 nm wavelength ranges. Nine different diodes were fabricated with optimal spacing of the peak emission wavelengths in order to have sufficient overlapping of their spectra. Efficient LEDs with narrow spectra have been realised by careful selection of the layer structure and growth conditions. Thick active layers with constant composition and abrupt interfaces have been grown for each emission wavelength. The long wavelength diodes (1275–1675 nm) were grown with additional quaternary layer(s) to prevent the melt-back of the active layer by InP melt. Low growth temperature (590°C) was used to prepare the LED structures. In the spectral range of 1250–1520 nm higher growth temperatures (625–645°C) were necessary to improve the device parameters. Such phenomena confirm the existence of the miscibility gap in the InGaAsP quaternary crystal system. Quaternary layers grown in the middle of the immiscibile region showed non-uniform composition and ragged interfaces at the upper heterojunction.

Growth of semi-insulating InP with uniform axial Fe doping by a double-crucible LEC technique

The level of an Fe-doped InP melt in a growth crucible is kept constant throughout a Czochralski growth experiment by replenishing it with undoped melt from a second crucible. Since the distribution coefficient of iron is very small (about 0.001), the Fe concentration in the growth crucible is virtually unchanged during the pulling. As a result the ingot obtained exhibits axial Fe concentration much more uniform than in standard LEC crystals. This growth method can increase the yield of semi-insulating InP wafers as it prevents the accumulation of iron and the formation of precipitates in the last to freeze part of the crystal.

Transport phenomena in a high pressure crystal growth system: In situ synthesis for InP melt

The physical phenomena underlying the “one-step” in situ synthesis and high pressure growth of indium phosphide crystals are complex. A high resolution computer model based on multizone adaptive grid generation and curvilinear finite volume discretization is used to predict the flow and temperature fields during the synthesis of the InP melt. Simulations are performed for a range of parameters, including Grashof number, crucible rotation, and location of the injector. These parameters affect the gas flow in a high pressure liquid-encapsulated Czochralski (HPLEC) furnace significantly, and have a strong influence on the melt synthesis and its control.

Study on microscopic defects in Fe-Doped InP single crystals

Effect of crystal growth conditions on the density of microscopic defects, observed on as-polished Fe-doped InP LEC single crystal wafers, has been investigated by an interference contrast microscope and a laser scattering tomography (LST) system. It was found that crystal rotation speeds affect the density of microscopic defects. In addition, the density depends on the duration for which the InP melt is held in molten state before crystal growth. On the other hand, it was found that the H/sub 2/O concentration in B/sub 2/O/sub 3/ has no correlation with the generation of microscopic defects. The relationship between the microscopic defects and the stoichiometry of grown crystals was investigated by coulometric titration analysis for the indium concentration. The density of microscopic defects is reduced as the indium concentration decreased. From the present results, it is speculated that the origin of microscopic defects is indium or indium oxide.

Analysis of Dopant Distributions in LEC‐InP

AbstractIt is often important to be able to estimate the concentration of dopant atoms incorporated into InP crystals grown from InP melt of given composition. In this paper we present a simple parameter (G) to revise the commonly used effective distribution coefficient (keff) and the Scheil equation. The results obtained for various dopants and different initial concentrations in LEC‐grown InP ingots are discussed. It is shown that the revised dopant concentration curves tally with the real distributions.

InP single crystal growth with controlled supercooling during the early stage by a modified LEC method

A new liquid encapsulated Czochralski (LEC) technique for InP single crystal growth has been developed. In order to restrain the generation of twin bondaries from the shoulder of InP crystal by the LEC method, at the beginning of InP crystal growth, we tried to produce growth toward the lateral direction until reaching a 2-inch diameter without forming a cone angle ( θ = 90°) by controlling the optimum supercooling of the InP melt. As a result, it was found that although isotropic growth could restrain the twin boundary, anisotropic growth was likely to generate a twin boundary at the completion of lateral growth. After isotropic growth, InP single, crystals were obtained reproducibly. That is, ten single crystal ingots of InP were obtained by this method. Furthermore, the etch pit density (EPD) of InP water with a 2-inch diameter was less than 2000 cm -2, except at the edge of the water, by Zn doping ((3.0-4.0) X 10 18 cm -3).

Channeling and photoluminescence studies of heat-treated InP single crystals

2 MeV α-particle channeling and photoluminescence investigations were carried out to study the effects of heat treatment on 〈100〉 InP single crystals heated in powdered InP or Sn-InP melt ambients at 500–550 ° C for various durations. Observations suggest two types of native defects: type I defects which quench luminescence and increase in concentration in a phosphorus-deficient environment, and type II defects which are responsible for changes in the minimum channeling yield. These latter type defects multiply during short annealing cycles, but reduce in concentration in the longer annealing cycles in both powdered InP and Sn-InP melt ambients.

Electrical Properties of Bulk InP Synthesized by Modified Horizontal Bridgman Method

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Growth and properties of InP single crystals grown by the magnetic field applied LEC method

Abstract The effect of a magnetic field on the properties of InP melt and grown crystals have been investigated. Temperature fluctuations in the melt were effectively reduced to less than 0.3°C at 1000 G. Neither irregular growth striations nor microscopic defects, such as “grappes” or dislocation clusters, were observed in the 50 mm diameter crystals grown under a magnetic field of 1000 G. A low etch pit density of 6 x 10 3 cm -2 was obtained on average for undoped crystals, and dislocation-free S-doped crystals co-doped with Ga and Sb were obtained under the magnetic field.