Zn In InP Research Articles

Phosphorus vacancy mediated complex diffusion mechanism of Zn in InP

Implantation and diffusion of Zn dopant into bulk InP:S were performed. Zn concentration profiles were investigated by secondary ion mass spectrometry and capacitance–voltage method. The influence of thermodynamic conditions of annealing on the diffusion mechanism of Zn atoms was observed and described. Excess phosphorus vacancies [VP] generation causes diffusion of Zn dopant by the zinc atom – phosphorus vacancy complex [VP – ZnIn – VP] producing a characteristic diffusion profile. Such electrically inactive zinc atom lattice site, cause a lower diffusion coefficient than that at a generally known interstitial-substitutional mechanism.

Tuning the onset pressure of pressure-induced phase transition in indium phosphide by extrinsic doping

In-situ angle-dispersive X-ray diffraction (ADXRD) and Raman scattering were carried out to delineate the phase transitions under pressure in p-type zinc-doped indium phosphide (InP:Zn) at ambient temperature. The ADXRD measurements with pressure up to 17.3(2) GPa reveal that InP:Zn transforms from zinc-blende (ZB) to rock-salt (RS) structure in a pressure range of 8.1(2) - 8.6(1) GPa. The Raman scattering measurements indicate that the phase transition proceeds continuously over a wide range of pressure and reaches completion at the highest pressure applied (14.5(2) GPa) with significant metallization, as suggested by the disappearance of the transverse optical (TO) and longitudinal optical (LO) modes. In contrast, originally absent at ambient pressure, additional Raman shift of Zn local vibrational modes (LVMs), appeared at 276 cm-1 and 420.7(1) cm-1 within the pressure range of 2.2(1) up to 10.1(2) GPa, which can be attributed to Zn3P2 and VPZnInVP LO modes, respectively. The zero-pressure isothermal bulk moduli and its first order pressure derivatives for the zinc-blende InP:Zn are 79.44(2) GPa and 3.92(1), respectively. A total enthalpy change of about 45.45 KJ•mole-1 was derived for the ZB to RS structure transformation occurring at the pressure of 8.6(1) GPa. The present results suggest that diffusion of Zn in InP:Zn may have been governed by the modified substitution and interstitial (S–I) mechanism. Moreover, comparisons on the pressure-dependent behaviors in InP:Zn, InP:S, and InP:Fe extrinsically doped systems revealed that the exact type of the defects introduced into the lattice upon doping may have played crucial roles in the pressure-induced phase transitions.

Effect of Zinc Incorporation on the Performance of Red Light Emitting InP Core Nanocrystals.

This report presents a systematic study on the effect of zinc (Zn) carboxylate precursor on the structural and optical properties of red light emitting InP nanocrystals (NCs). NC cores were assessed using X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), energy-dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HRTEM). When moderate Zn:In ratios in the reaction pot were used, the incorporation of Zn in InP was insufficient to change the crystal structure or band gap of the NCs, but photoluminescence quantum yield (PLQY) increased dramatically compared with pure InP NCs. Zn was found to incorporate mostly in the phosphate layer on the NCs. PL, PLQY, and time-resolved PL (TRPL) show that Zn carboxylates added to the precursors during NC cores facilitate the synthesis of high-quality InP NCs by suppressing nonradiative and sub-band-gap recombination, and the effect is visible also after a ZnS shell is grown on the cores.

Diffusion mechanism of Zn in InP and GaP from first principles

The diffusion mechanism of Zn in GaP and InP has been investigated using first-principles computational methods. It is found that the kickout mechanism is the favored diffusion process under all doping conditions for InP, and under all except $n$-type conditions for GaP. In $n$-type GaP the dissociative mechanism is probable. In both $p$-type GaP and InP, the diffusing species is found to be ${\mathrm{Zn}}_{i}^{+2}$. The activation energy for the kickout process is $2.49\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ in GaP and $1.60\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ in InP, and therefore unintentional diffusion of Zn should be a larger concern in InP than in GaP. The dependence of the activation energy both on the doping conditions of the material and on the stoichiometry is explained, and found to be in qualitative agreement with the experimentally observed dependencies. The calculated activation energies agree reasonably with experimental data, assuming that the region from which Zn diffuses is $p$ type. Explanations are also found as to why Zn tends to accumulate at $pn$ junctions in InP and to why a relatively low fraction of Zn is found on substitutional sites in InP.

Diffusion and activation of Zn implanted into InP:S

The aim of this work is to compare carrier concentration, diffusion coefficient and shape of the zinc atomic profile in InP layers treated under different annealing conditions. Zn implanted InP:S (4×10 18 at/cm 3—active dopant) bulk samples were investigated. Samples were implanted to a fluence of 1×10 16 cm −2 at an energy of 150 keV and then coated with a 100 nm thick AlN polycrystalline film, using sputter deposition followed by annealing at temperatures in the range 500–900 °C for various different conditions. After removal of the AlN films the extent of diffusion of the implanted species was characterized using the SIMS (Secondary Ion Mass Spectrometry) technique whilst carrier concentration was evaluated by C– V profiling. The depth profiles of in-diffused zinc strongly indicated that the diffusion coefficient D was concentration-dependent. The diffusivity of Zn was found largest when InP was annealed with phosphorus overpressure combined with the AlN cap; in case of annealing at 700 °C a Zn concentration of 2×10 19 cm −3 was achieved. The diffusion range under phosphorus overpressure was almost twice that in vacuum and this is interpreted in terms of the generation of additional vacancies in the In sub-lattice. C– V measurements showed clearly that application of protective AlN together with phosphorus overpressure causes sulphur donors compensation and results in acceptor concentration of 1×10 18 cm −3 and consequently, in the formation of a well-defined p–n junction. The activation efficiency of Zn atoms can be estimated to be about 30%, without additional heat treatment. The Boltzmann–Matano analysis was employed to evaluate the concentration-dependent diffusion coefficient of Zn in InP.

Effect of the carrier gas and the group-V precursor on the DEZn doping efficiency for InP and In 0.54Ga 0.46As in LP-MOVPE

The effect of the carrier gases H 2 or a N 2/H 2 (90%/10%) mixture with the group-V precursors TBA, TBP, PH 3 and AsH 3 on the distribution coefficient of Zn in InP and In 0.54Ga 0.46As has been investigated. Changing from PH 3 to TBP as the group-V precursor increases the incorporation efficiency of Zn, whereas the opposite effect is observed for the change from AsH 3 to TBA. Furthermore, for In 0.54Ga 0.46As and InP the distribution coefficient of Zn increases and is less sensitive to V/III ratio variations when using N 2/H 2 (90%/10%) as carrier gas instead of H 2.

Far-infrared spectroscopy of the zinc acceptor in indium phosphide

We report the absorption spectrum of Zn acceptor in InP. Fourier interferometers equipped with Si bolometers were used to collect spectra at sample temperatures down to 1.9 K. Zeeman measurements were made in the Voigt configuration at fields up to 6.5 T with the electric field of the radiation, E , polarised either parallel or perpendicular to the magnetic field, B||〈001〉 . Energies for the G and D lines, corresponding to transitions from the 1 s 3/2 (Γ 8 +) to the 2 p 3/2 (Γ 8 −) and 2 p 5/2 (Γ 8 −) states, respectively, are 241.5±0.2 and 286.0±0.2 cm −1, respectively. Data taken at higher resolution (0.05 cm −1) indicate an intrinsic line width of 0.5 cm −1 full-width at half-maximum for a carrier concentration of 4×10 16 cm −3. At low magnetic field ( B<3 T), the D line rapidly broadens, losing intensity and becoming unresolvable. At the highest fields, four components for E|| B and two for E ⊥ B are resolved for the G line. Comparing data at 1.9, 2.9, 5.4 and 10.4 K reveals thermal depopulation effects. These experimental data permit determination of g-factors for the ground and first excited state of Zn in InP.

Experimental studies of the initial diffusion stage in semiconductors

The initial diffusion stage (IDS) of B in Si and Zn in III–V compounds has been studied. The ultra-fast diffusion of Zn in InP has been found at low temperature. An evolution of non-equilibrium defect has been investigated during both IDS and isothermal diffusion. A mechanism of the processes going on IDS has been proposed.

Wafer fused p-InP/p-GaAs heterojunctions

This article reports on the fabrication and characterization of wafer fused heterojunctions between p-InP and p-GaAs. Secondary ion mass spectroscopy was used to characterize doping profiles across the interface as well as the interface contamination with oxygen or carbon. The crystalline quality of the fused material was characterized using cross section and plan-view transmission electron microscopy. The electrical properties of the fused interface were studied as a function of various doping elements such as Be and Zn in InP or Zn and C in GaAs as well as for different acceptor concentrations in GaAs. Finally, the electrical characteristics were analyzed using a numerical model that includes thermionic emission and tunneling across the heterobarrier.

Threshold Character of Zn Diffusion into InP

ABSTRACTThe initial diffusion stage (lIDS) of Zn in InP from polymer spin-on films has been investigated. The threshold diffusion temperature of 375°C has been established. It has been found that the heavily-doped near-surface layer, that consisted of electrically neutral zinc-containing complexes, was formed at IDS, while a low part of Zn was electrically active. The Zn diffusivity during IDS has been found to be at least two orders of magnitude more than the Zn diffusivity obtained after an isothermal diffusion.

Subpicosecond carrier lifetime in InP

Femtosecond time-resolved reflectivity investigations reveal a significant reduction in carrier lifetime from 100ps in nonintentionally doped InP to less than 1ps in S, Fe, and Zn doped InP. This reduction is because S, Fe, and Zn in InP serve as recombination and trapping centers. Photoluminescence and Raman measurements were used to confirm these results.

A comparison of TMGa and TEGa for low-temperature metalorganic chemical vapor deposition growth of CCI4-doped inGaAs

Factors which influence the alloy composition and doping level of CCl4-doped In0.53Ga04.7As grown at low temperatures (450°C < Tg < 560°C) by low-pressure metalorganic chemical vapor deposition (MOCVD) have been investigated. The composition is highly dependent on substrate temperature due to the preferential etching of In from the surface during growth and the temperature-dependent growth efficiency associated with the Ga source. The lower pyrolysis temperature of TEGa relative to TMGa allows the growth of CCl4-doped InGaAs at lower growth temperatures than can be achieved using TMGa, and results in improved uniformity. High p-type doping (p ∼ 7 × 1019 cm-8) has been achieved in C-doped InGaAs grown at T = 450°C. Secondary ion mass spectrometry analysis of a Cdoping spike in InGaAs before and after annealing at ∼670°C suggests that the diffusivity of C is significantly lower than for Zn in InGaAs. The hole mobilities and electron diffusion lengths in p+-InGaAs doped with C are also found to be comparable to those for Be and Zn-doped InGaAs, although it is also found that layers which are highly passivated by hydrogen suffer a degradation in hole mobility. InP/InGaAs heterojunction bipolar transistors (HBTs) with a C-doped base exhibit high-frequency performance (ft = 62 GHz, fmax=42 GHz) comparable to the best reported results for MOCVD-grown InP-based HBTs. These results demonstrate that in spite of the drawbacks related to compositional nonuniformity and hydrogen passivation in CCl4-doped InGaAs grown by MOCVD, the use of C as a stable p-type dopant and as an alternative to Be and Zn in InP/ InGaAs HBTs appears promising.

Photoluminescence studies of interstitial Zn in InP due to rapid thermal annealing

Deep donor to acceptor transitions between interstitial and substitutional Zn in InP are investigated in this study via the photoluminescence technique. Interstitial Zn is to be fully activated when treated by rapid thermal annealing process at 600 °C. When treated at 400 °C, however, interstitial Zn is partially activated so that medium distance deep donor-to-acceptor transitions become less available. This medium distance transition is estimated to be in a range between 35 and 60 Å.

Lattice Site Localization of Zn in InP Using the PIXE/Channeling Technique

The lattice position of Zn in InP is investigated using PIXE (proton-induced X-ray emission) combined with the channeling technique. The total Zn concentration is 1.3 × 1020 cm−3 About 90% of the in-diffused Zn atoms are located at tetrahedrally coordinated interstitial sites. The free carrier concentration is one order of magnitude lower than the number of substitutional Zn atoms. Precipitates are not found by the channeling technique. After heat treatment in a Zn-free atmosphere the surface zinc concentration decreases to 1 × 1019 cm−3 and nearly 90% of the diffused Zn atoms reside on regular lattice sites. The free carrier concentration increases from 2 × 1018 cm−3 after diffusion and before annealing to 9 × 1018 cm−3 after annealing. Aus PIXE (protoneninduzierte Rontgenemission)-Messunge kombiniert mit der Channeling-Technik werden Gitterplatzpositionen von Zn in InP untersucht. Die Gesamtzinkkonzentration betragt 1.3 × 1020 cm−3. Etwa 90% der eindiffundierten Zn-Atome werden auf tetraedrisch koordinierten Zwischengitterplatzen gefunden. Die Zahl der freien Ladungstrager ist eine Grosenordnung kleiner als die Anzahl der substitutionell eingebauten Zn-Atome. Prazipitate werden mit der Channeling-Technik nicht gefunden. Nach einem Temperschritt in Zn-freier Atmosphare fallt die Zn-Konzentration auf 1 × 1019 cm−3 und ungefahr 90% der diffundierten Zn-Atome werden auf regularen Gitterplatzen nachgewiesen. Die Konzentration der freien Ladungstrager steigt von 2 × 1018 cm−3 nach der Diffusion und vor dem Tempern auf 9 × 1018 cm−3 nach dem Tempern.

Rapid thermal processing of zinc diffusion in indium phosphide

A stripe heater has been used to diffuse zinc into semi-insulating and n-type (001) InP from a thin spun-on zinc silica film. The diffusion profiles were investigated by means of secondary ion mass spectroscopy and capacitance-voltage measurements. Diffusion depth and activation energy of an effective diffusion coefficient are compared with those published for Zn ampoule diffusion. For the diffusion of Zn in semi-insulating InP an activation energy of 1.35 eV was found. An expression for the effective diffusion coefficient for Zn in InP is derived and compared with results of a Boltzmann-Matano analysis of diffusion profiles. As a result the zinc diffusion can be described by the interstitial-substitutional model, where Zn diffuses as a singly positive charged interstitial and acts as an acceptor by filling an In vacancy.

MOVPE in GaInAsP systems for opto-electronic applications

We have studied the capabilities of the growth of quantum well structures in the GaInAsP material system by metalorganic vapor phase epitaxy (MOVPE) for optical applications. In particular we discuss the interfacial structure and the reproducibility of growth for InP/GaInAs, GaInAsP/GaInAs and InP/GaInAsP quantum well structures as well as the controlled n- and p-type doping, which are the most crucial steps in depositing opto-electronic devices based on quantum wells. It is shown by photoluminescence, X-ray diffractometry and absorbtion spectroscopy that the compositional grading at the interfaces does not exceed 2 monolayers and that the interfaces are atomically flat. The presented data strongly indicate a 2-dimensional mode of growth leading to an exact control of the well and barrier widths. In addition extensive study of the Zn doping mechanisms reveals diffusion coefficients of Zn in InP as low as 6.5 x 10 −14 cm 2/s. The capabilities of the developed MOVPE growth process are demonstrated for GaInAs/GaInAsP separate confinement heterostructure lasers with GaInAs well widths of only 4 monolayers. The lasers emit at 1.3 μm at a threshold current density of 0.78 kA/cm 2.

Effects of S, Si, or Fe dopants on the diffusion of Zn in InP during MOCVD

Diffusion of Zn in InP during growth of InP epitaxial layers has been investigated in layer structures consisting of Zn-InP epilayers grown on S-InP and Fe-InP substrates, and on undoped InP epilayers. The layers were grown by metalorganic chemical vapour deposition (MOCVD) atT = 625° C andP = 75 Torr. Dopant diffusion profiles were measured by secondary ion mass spectrometry (SIMS). At sufficiently high Zn doping levels ([Zn] ≥8 × 1017 cm−3) diffusion into S-InP substrates took place, with accumulation of Zn in the substrate at a concentration similar to [S]. Diffusion into undoped InP epilayers produced a diffusion tail at low [Zn] levels, probably associated with interstitial Zn diffusion. For diffusion into Fe-InP, this low level diffusion produced a region of constant Zn concentration at [Zn] ≈ 3 × 1016 cm−3, due to kick-out of the original Fe species from substitutional sites. We also investigated diffusion out of (Zn, Si) codoped InP epilayers grown on Fe-InP substates. The SIMS profiles were characterised by a sharp decrease in [Zn] at the epilayer-substrate interface; the magnitude of this decrease corresponded to that of the Si donor level in the epilayer. For [Si] ≫ [Zn] in the epilayer no Zn diffusion was observed; Hall measurements indicated that the donor and acceptor species in those samples were electrically active. All these results are consistent with the presence of donor-acceptor interactions in InP, resulting in the formation of ionised donor-acceptor pairs which are immobile, and do not contribute to the diffusion process.

Comparison of Zn and Mg incorporation in MOVPE InP/GaInAsP laser structures

The objective of this work is to study the incorporation process of Zn in InP and related ternary and quaternary layers for long wavelength laser applications in comparison with the alternative acceptor Mg. In InP above a critical concentration of (1–2)×1018 cm−3 a sudden onset of dopant diffusion during growth is observed for Zn and for Mg as well. This diffusion during growth can be markedly reduced by counter-doping with Si (Fermi level effect). Below the critical concentration Zn dopant profiles exhibit the same steep flanks as Mg dopant profiles suggesting the same low diffusion coefficients. However, Zn appears to be more suitable forp-type doping of InP, GaInAs and GaInAsP, because an accurate control of the dopant level in the epitaxial layers is easier to achieve with Zn than with Mg.

Photoluminescence of Zn-diffused and annealed InP

Ampoule diffusion of Zn in InP gives rise to donor-acceptor photoluminescence transitions with peak positions dependent on the rate of cooling after diffusion. Subsequent annealing in an atmosphere without Zn causes a change in peak position. Luminescence peaks between 1.30 and 1.38 eV are found. These peaks are described as being due to transitions between various Zn interstitial donor levels and the Zn substitutional acceptor level. The luminescence results are correlated with results of secondary ion mass spectrometry and Schottky barrier capacitance-voltage measurements, and are consistent with an earlier model in which Zn diffuses as an interstitial donor and is incorporated both as an interstitial donor and as a substitutional acceptor.

The behaviour of Zn in InP and InGaAsP studied by SIMS

Congenital sucrase-isomaltase (SI) deficiency is an autosomal-recessive intestinal disorder characterized by a drastic reduction or absence of sucrase and isomaltase activities. Previous studies have indicated that single mutations underlie individual phenotypes of the disease. We investigated whether compound heterozygous mutations, observed in some patients, have a role in disease pathogenesis.We introduced mutations into the SI complementary DNA that resulted in the amino acid substitutions V577G and G1073D (heterozygous mutations found in one group of patients) or C1229Y and F1745C (heterozygous mutations found in another group). The mutant genes were expressed transiently, alone or in combination, in COS cells and the effects were assessed at the protein, structural, and subcellular levels.The mutants SI-V577G, SI-G1073D, and SI-F1745C were misfolded and could not exit the endoplasmic reticulum, whereas SI-C1229Y was transported only to the Golgi apparatus. Co-expression of mutants found on each SI allele in patients did not alter the protein's biosynthetic features or improve its enzymatic activity. Importantly, the mutations C1229Y and F1745C, which lie in the sucrase domains of SI, prevented its targeting to the cell's apical membrane but did not affect protein folding or isomaltase activity.Compound heterozygosity is a novel pathogenic mechanism of congenital SI deficiency. The effects of mutations in the sucrase domain of SIC1229Y and SIF1745C indicate the importance of a direct interaction between isomaltase and sucrose and the role of sucrose as an intermolecular chaperone in the intracellular transport of SI.