InP Samples Research Articles

Coupled time resolved and high frequency modulated photoluminescence probing surface passivation of highly doped n-type InP samples

Electronic passivation of III–V surfaces is essential for applications in optoelectronic devices. A key aspect is the measurement of the surface recombination properties, which can be done by various techniques including transient photoluminescence (TRPL) or luminescence quantum yield. These measurement techniques are always indirect since they suppose postulating a mathematical model for the data interpretation. Most common models use the notion of surface recombination velocity to quantify the surface recombination. In this paper, we demonstrate on the InP substrate that this notion is not always sufficient to represent the injection dependence of the surface phenomena. The study of power dependence of TRPL decays coupled with modulated photoluminescence (MPL) spectra on four samples from the same wafer with different surface treatments (epi-ready, freshly cleaned, after air exposure, and with poly-phosphazen passivation) allows us to discriminate between bulk and surface properties. We introduce surface defect trapping as an alternative to explain TRPL decays and MPL phase excitation power dependences of the three non-passivated samples. Surface trap parameters such as capture cross section and defect density are extracted. The passivated sample exhibits an invariant response shape on eight orders of magnitude of illumination. The stability of the PL response at high flux is in agreement with the perfect stability of the passivation layer, which is able to protect the InP surface without chemical changes over more than one year. They are linked to the nature of the passivation layer/InP interface. Other surface treatments were found to have an injection dependent response at high flux corresponding to different surface defect distributions but also possibly to surface chemical changes for the freshly cleaned sample.

Preparation and novel photoluminescence properties of the self-supporting nanoporous InP thin films

Self-supporting nanoporous InP membranes are prepared by electrochemical etching, and are then first transferred to highly reflective (> 96%) mesoporous GaN (MP-GaN) distributed Bragg reflector (DBR) or quartz substrate. By the modulation of bandgap, the nanoporous InP samples show a strong photoluminescence (PL) peak at 541.2 nm due to the quantum size effect of the nanoporous InP structure. Compared to the nanoporous InP membrane with quartz substrate, the nanoporous membrane transferred to DBR shows a twofold enhancement in PL intensity owing to the high light reflection effect of bottom DBR.

Воздействие некоторых сложных хемостимуляторов и модификаторов на термооксидирование InP

Воздействие некоторых сложных хемостимуляторов и модификаторов на термооксидирование InP

Plasma Surface Preparation of III-V Materials: Quasi In-Situ XPS Measurements and Integration Guidelines

Obtaining a competitive III-V laser made with a CMOS-compatible process is a major issue in the framework of Silicon photonics. The choice of the material used to elaborate an ohmic contact for III-V substrate is quite limited and fabrication processes need to be developed [1, 2]. In this way, the surface preparation of the substrate before any deposition is the first step necessary towards success [3]. The native oxides need to be removed and the surface should not be damaged. A wet cleaning is used to remove the oxides and contaminants on the substrate surface, but the oxide regrowth occurs during the vacuum break undergone between the wet cleaning and the deposition reactor. Therefore, in-situ plasma cleaning is a mandatory complement in order to remove the substrate oxides before the deposition [3]. Helium and Argon plasma treatments have been used in this study on InGaAs and InP materials. Quasi in-situ analysis is ensured with the use of a vacuum wafer carrier [4]. Inbulk, InOx, InIn-In, Pbulk and POx concentrations have been extracted from In 3d5/2 and P 2p3/2 core level energy regions [5, 6]. Figure 1 shows the parallel angle-resolved XPS (pAR-XPS) measurements of the P 2p energy region of an InP substrate after an He plasma. Transport to the XPS have been completed with and without the use of the vacuum wafer carrier. Measurements have been performed at a collection angle of 55 ± 5° corresponding to the middle range (roughly 2-3 nm). Pbulk and Pox proportions correspond to the sum of the two doublets 3/2 and 1/2 of the phosphorus core level energy region respectively for the P-In and P-O bindings. Pox proportion is higher when an air vacuum break of 30 minutes occurs (Fig.1) whereas this concentration is almost zero using the vacuum wafer carrier. Thanks to the use of quasi in-situ XPS analysis, the removal of Pox (Fig.1) on InP is clearly demonstrated which was not the case in a previous study where an air vacuum break was realized between the surface treatment and the XPS analysis [3]. Thus, quasi in-situ characterization improves the accuracy of the results notably by limiting the oxides regrowth occurring during the wafer transfer (Fig. 1). Figure 2 and 3 show a summary of pAR-XPS measurements realized on InP samples after various plasma treatments. XPS spectra have been collected at angles of 25 ± 5° and 75 ± 5°, corresponding to photoelectrons escaping from the bulk surface (roughly 10 nm) (Fig.2) and the surface (roughly 1 nm) (Fig.3) . Two Argon plasma conditions were used. “Ar plasma soft” corresponds to the less powerfull recipe. InP substrate “as-received” was measured to determine oxide proportions of both elements, 21% for POx and 68.1% for InOx. Looking at the deep surface measurements (Fig.2), all plasma exhibit interesting results for the oxide removal. In-In bonds are created during the cleaning and may be assimilated to indium agglomerates at the InP surface [3]. Comparison with results in the near surface (Fig.3) shows that “Ar plasma” is the most efficient for the oxide removal with Pox and Inox proportions at 11.2% and 25.7%. “He plasma” is also effective but shows an higher Pox proportion close to the surface (23.7%). “Ar plasma soft” clearly shows the highest oxide proportions near the surface with Pox and Inox at 16.3% and 34.3%. From this study, it can be concluded that Ar and He plasmas are suitable candidates for the surface preparation of III-V materials prior to metallization. Moreover, the benefit to work with a quasi in-situ characterisation has been established. Measurements obtained give more accuracy to monitor the plasma surface preparation performance (Fig. 1). This work was supported by the French National Research Agency (ANR) under the ”Investissements d’avenir” programs: ANR 10-AIRT-0005 (IRT NANO-ELEC), ANR 10-EQPX-0030 (EQUIPEX FDSOI 11) and ANR-10-EQPX-0033 (EQUIPEX IMPACT). [1] L. Grenouillet, and al., 6th IEEE Int. Conf. on Gr. IV Photonics, 2009. [2] E. Ghegin, and al., EEE Trans. on Elect. Dev., vol. 64, n° 111, pp. 4408, 2017. [3] Ph. Rodriguez and al., ECS Trans., vol. 69, n° 18, pp. 251, 2015. [4] B. Pelissier and al., Microelec. eng., vol. 85, n° 11, pp. 151, 2008. [5] G. Hollinger and al., J. of Vac. Sci. & Tech. A: Vac., Surf., and Films, vol. 3, n° 16, pp. 2082, 1985. [6] G. Bruno and al., J. de Physique IV, vol. 5, n° C5, pp. 663, 1995. Figure 1

High performance In0.83Ga0.17As SWIR photodiode passivated by Al2O3/SiNx stacks with low-stress SiNx films

To develop extended InGaAs photodiode focal plane arrays with large scale and small pixels, a surface passivation film with low stress is necessary. To study the surface bowing of SiNx passivation film deposited with different conditions by inductively coupled plasma chemical vapor deposition, 2-in. InP samples were first utilized to obtain statistical results. As can be seen from the result, the bowing introduced by the passivation film is reduced to less than 10 μm when applying optimized film deposition conditions, which is a significant optimization. In the further investigation of the passivation effect on the InGaAs photodiode, Al2O3/SiNx stacks were proposed as the passivation layer, and Al2O3 was deposited by atomic layer deposition (ALD). Results demonstrate that the photodiodes passivated by the Al2O3/SiNx stacks have lower dark current density, especially at lower temperatures. At 180 K, the contribution of perimeter dark current is reduced by more than one order of magnitude. Theoretical analysis shows that the composite passivation film effectively suppresses tunneling current at 180 K.

Band Alignment of N- and P- Doped InP at Electrolyte and Ultra High Vacuum Junctions: Fundamental Correlation between the Open Circuit Potential Under Illumination and XPS Photopeak Energy

Electrochemistry measurements have provided in-situ studies of surface and interfaces at the semiconductor / electrolyte junction. It has required monitoring the current/voltage responses at the semiconductor/ electrolyte interface associated with impedance measurements. In this work, energy band diagram of InP has been given by determining Fermi level (work function), conduction band (electron affinity) and valence band positions. They have been referred by a theoretical absolute scale with vacuum level as a reference point. The electrochemical potential of electrons is given by Nernst equation according to an electrochemical reference electrode. The solid state scale at 0 eV and the electrochemical scale have been offset from one another by a defined voltage according to the reference electrode. For example 0 eV corresponded to -4.5 V vs. NHE (Normal Hydrogen Electrode) or -4.46 V SCE (Sulfate Calomel Electrode). The contact between InP and the electrolyte acted as a liquid schottky junction providing the equalization of both Fermi levels giving rise to the electrolyte work function. In the dark at open circuit potential conditions (Voc), the equilibrium junction of InP/aqueous electrolyte made InP Fermi level in depletion region. For this band bending, the Boltzmann relation described the distribution of electrons in the space charge region and the electric field was determined by Gauss’ law. Poisson’s equation could be solved within that region to give the Mott–Schottky equation. For both -n and –p doped InP, flat band potentials and the doping levels were deduced from the resulting linear straight lines of the C-2(V) curves. The energy band diagram using –n and –p types InP was accurately deduced. Another interesting interfacial features are the open circuit potentials in dark and under illumination. They reflect on -n and -p type the electronic transfer processes associated to the junction building. Under illumination the variation of Voc (ΔVoc) between both types vs illumination intensity is related to the equilibrium evolution due to hole / electron distribution through the junction under light perturbation. Figure 1 shows the Voc separation from the dark (ΔVoc~ 130mV) and for the highest illumination condition (ΔVoc~ 550mV). Highest separation should be obtained by still increasing the light power. Note that in this case the electrolyte is diluted with sulfuric acid (0.5M), which maintains a perfect oxide free interface. This gives rise to a perfect reversibility of Voc between the dark and illuminated situations contrary to observations which have been already studied in neutral pH [1]. Similar access to the absolute energy diagram of -n and -p InP samples can be observed in Ultra High vacuum condition (UHV). As for liquid junction an absolute energy position towards the Fermi level of an X-ray Photoelectron Spectrocopy spectrometer (XPS) can be observed. Figure 2 shows the binding energy position variation of core levels for -n and -p InP samples. Again the surfaces are oxide free. The variation between -n and -p is around 0.7eV corresponding again to samples submitted to strong illumination due in this case to X-rays flux. Even if the junction has been under high vacuum, persuasive analogies have been observed between the variation of Fermi level at open circuit potential under illumination and their respective relative position by XPS. Specific band bending at interfaces UHV/SC and Liquid/SC are compared and discussed through the data obtained by interfacial electrochemistry and XPS considerations. [1] J. C. Meldeje, A.-M.Gonçalves, N. Simon, L. Ouattara, A. Etcheberry. J. of Electrochem. Soc. 165 (4) H3138-H3142 (2018) Figure 1

Surface passivation of InP using an organic thin film

We demonstrate the surface passivation of InP using thin layers of a perylenetetracarboxylic diimide derivative (PTCDI-C9) applied via organic vapor phase deposition (OVPD). The organic layer forms a conformal crystalline film on the InP surface, which is confirmed by atomic force microscopy and X-ray diffraction. Area-dependent photoluminescence measurements indicate that the coating reduces surface recombination. The organic thin film deposited by OVPD exhibits improved photoconductivity compared to an unpassivated InP sample, and to a layer deposited via vacuum thermal evaporation. Our results suggest that semiconductor surface passivation using organic thin films deposited by OVPD has applications to a variety of optoelectronic devices, particularly with structures requiring sidewall or conformal coatings.

Enhanced RadOptic sensitivity in intrinsic bulk InP

RadOptic detectors are a promising method to record MeV pulsed radiation for inertial confinement fusion diagnostics. Because of the low radiation-induced refractive index change sensitivity of semiconductors, these detectors have poor responses to MeV gamma pulses. An enhancement of the radiation-refractive index change sensitivity in an InP sample is reported. The refractive index change of the InP sample was recorded by a plate interferometer. The probe laser had a wavelength of 1550 nm (0.8 eV). The excess carrier density was obtained using the refractive index modulation theory and evolution model. For the InP sample, the excess carrier density calculated using the refractive index change was much higher than the excess density calculated by the evolution model. This suggested that the refractive index change of the InP sample is more sensitive to the excess carrier density. The enhancement was attributed to the inter-conduction transition from the Γ valley to the X valley (Γ→X, 0.78 eV). In addition to enhancing the energy deposition efficiency, the radiation-refractive index change sensitivity of RadOptic sensors can also be enhanced by extra absorptions arising from inter-conduction band transitions.

Positron affinity and bulk lifetime and positronium work function in indium phosphide under pressure

The electron and positron chemical potentials, positron affinity and bulk lifetime as well as the positronium work function in InP are investigated. The emphasis of this work is on the hydrostatic pressure effect on these features. The calculations are performed with a pseudopotential approach and the independent particle model. All parameters of interest are found to vary monotonically with pressure. Our findings showed that under compression the positron annihilates differently in InP semiconductor compound. At zero pressure, the positron bulk lifetime is calculated to be 243.47 ps. However, upon compression it decreases almost linearly suggesting the decrease of the crystal ionicity under applied pressure. The positronium work function is found to increase with raising pressure which indicates that under compression less positronium atoms will be formed in InP sample surface and ejected into the vacuum. The parameters investigated in the present work are important in slow-positron-beam experiments.

Изучение сверхструктуры в сильно легированном пористом фосфиде индия рентгеновскими методами

AbstractAn indium-phosphide InP sample subjected to the pore-generation procedure and then doped with S atoms is studied by the methods of X-ray diffraction analysis (XRD) and small-angle X-ray scattering (SAXS) (with Cu K _α1-radiation). The XRD data demonstrate that the sample consists of (coherent) aligned homogeneous components. A point detector is used to obtain, in the anomalous transmission mode by Borrmann, a set of SAXS curves at sample positions varied by azimuthal rotations. The SAXS data are used to simulate a 2D SAXS pattern for the sample under study, which makes it possible to determine the long-distance translation symmetry and, consequently, the presence of a superstructure. The interplanar distances in the superstructure in the directions (110) and (1 0) of the InP lattice are found to be ~260 and 450 nm, respectively. The symmetry group of the superstructure is determined as C _2 v in the (001) plane of the sample lattice.

X-Ray Study of the Superstructure in Heavily Doped Porous Indium Phosphide

An indium-phosphide InP sample subjected to the pore-generation procedure and then doped with S atoms is studied by the methods of X-ray diffraction analysis (XRD) and small-angle X-ray scattering (SAXS) (with CuKα1-radiation). The XRD data demonstrate that the sample consists of (coherent) aligned homogeneous components. A point detector is used to obtain, in the anomalous transmission mode by Borrmann, a set of SAXS curves at sample positions varied by azimuthal rotations. The SAXS data are used to simulate a 2D SAXS pattern for the sample under study, which makes it possible to determine the long-distance translation symmetry and, consequently, the presence of a superstructure. The interplanar distances in the superstructure in the directions (110) and (1 0) of the InP lattice are found to be ~260 and 450 nm, respectively. The symmetry group of the superstructure is determined as C2v in the (001) plane of the sample lattice.

Optical properties of Zn-diffused InP layers for the planar-type InGaAs/InP photodetectors * * Project supported by the Key R&D Program of Jiangsu Province (No. BE2016085) , the National Natural Science Foundation of China (Nos. 61674051), and the External Cooperation Program of BIC, Chinese Academy of Sciences (No. 121E32KYSB20160071).

Zn diffusion into InP was carried out ex-situ using a new Zn diffusion technique with zinc phosphorus particles placed around InP materials as zinc source in a semi-closed chamber formed by a modified diffusion furnace. The optical characteristics of the Zn-diffused InP layer for the planar-type InGaAs/InP PIN photodetectors grown by molecular beam epitaxy (MBE) has been investigated by photoluminescence (PL) measurements. The temperature-dependent PL spectrum of Zn-diffused InP samples at different diffusion temperatures showed that band-to-acceptor transition dominates the PL emission, which indicates that Zn was commendably diffused into InP layer as the acceptor. High quality Zn-diffused InP layer with typically smooth surface was obtained at 580 °C for 10 min. Furthermore, more interstitial Zn atoms were activated to act as acceptors after a rapid annealing process. Based on the above Zn-diffusion technique, a 50 μm planar-type InGaAs/InP PIN photodector device was fabricated and exhibited a low dark current of 7.73 pA under a reverse bias potential of −5 V and a high breakdown voltage of larger than 41 V (I < 10 μA). In addition, a high responsivity of 0.81 A/W at 1.31 μm and 0.97 A/W at 1.55 μm was obtained in the developed PIN photodetector.

Addressing the electronic properties of III–V nanowires by photoluminescence excitation spectroscopy**This article belongs to the special issue: Emerging Leaders, which features invited work from the best early-career researchers working within the scope of J. Phys. D. This project is part of the Journal of Physics’ series 50th anniversary celebrations in 2017. Marta De Luca was selected by the Editorial Board

Semiconductor nanowires (NWs) have been attracting an increasing interest in the scientific community. This is due to their peculiar filamentary shape and nanoscale diameter, which renders them versatile and cost-effective components of novel technological devices and also makes them an ideal platform for the investigation of a variety of fascinating physical effects. Absorption spectroscopy is a powerful and non-destructive technique able to provide information on the physical properties of the NWs. However, standard absorption spectroscopy is hard to perform in NWs, because of their small volume and the presence of opaque substrates. Here, we demonstrate that absorption can be successfully replaced by photoluminescence excitation (PLE). First, the use of polarization-resolved PLE to address the complex and highly-debated electronic band structure of wurtzite GaAs and InP NWs is shown. Then, PLE is used as a statistically-relevant method to localize the presence of separate wurtzite and zincblende NWs in the same InP sample. Finally, a variety of resonant exotic effects in the density of states of InxGa1−xAs/GaAs core/shell NWs are highlighted by high-resolution PLE.

A comparative electrical transport study on Cu/n-type InP Schottky diode measured at 300 and 100 K

Two oxygen plasma treated InP samples with different plasma powers of 100 and 250 W were prepared and a comparative study on the electrical properties of Cu/n-type InP Schottky diode measured at 300 and 100 K was performed to investigate the current transport mechanism in detail. The forward and reverse bias current–voltage (I–V) characteristics were analyzed with considering various transport models. The fitting to the forward bias I–V characteristics revealed that relatively high ideality factor at 300 K for untreated sample were related with the generation-recombination (GR) current and the large E00 value at 100 K for 100 W plasma treated sample were associated with more significant tunneling effect. The analyses on the reverse bias current characteristics showed the suitable current transport model has changed from thermionic emission (TE) to TE combined with barrier lowering for both untreated and 250 W treated samples and from TE + BL to thermionic field emission for 100 W treated sample with increasing temperature from 100 to 300 K.

Photoelectrochemical Studies and Capacitance Measurements during the Nitride Passivation of InP in Liquid Ammonia (-55°C)

This work presents a fundamental photo-electrochemical process at the interface SC/electrolyte. The photoelectrochemical passivation of n-InP is reported in liquid ammonia (-55 °C) during an anodic treatment[1]. The extraction of InP sample from the solvent is successfully performed at ambient temperature. Thanks to XPS (X-ray Photoelectron Spectroscopy), a reproducible polyphosphazene like film is reported on InP (-[(H2N)-P=N]n-)[2]. A soft anodic electrochemical treatment under illumination is applied at the interface to provide a gradual controlled coverage ratio of the surface by the film. This quantitative study requires a chronopotentiometry process with a constant anodic current of 1µA.cm-2 under illumination. An anodic charge around 0.3 mC.cm-2 is enough to ensure a complete coverage of the surface by the film. According to the anodic charge a gradual striking flat band potential shift is observed (Fig. 1). A flat C-2 = f(V) is extended over 1 volt leading to a high interfacial capacitance (» 2µF.cm-2). From the analysis of capacitance-potential curves, the interface appears to be under accumulation conditions after the film formation. A significant drop of the resulting photo potential is then observed (Fig. 2). However, under a strong positive overvoltage (» 1V), a stationary anodic photocurrent is recovered. [1] A-M. Gonçalves, N. Mézailles, C. Mathieu, P. Le Floch, A. Etcheberry, « «Fully Protective yet functionalizable monolayer onto InP” Chemistry of Materials.22(2010) 3114-3120. [2] A-M. Gonçalves, C.Njel, C. Mathieu, D.Aureau, A. Etcheberry. « Phosphazene like film formation on InP in liquid ammonia (223K) . Thin Solid Films 538 (2013) 21–24. Figure 1

Combined influence of chemostimulator oxides V2O5 and MnO2 introduced via the gas phase on InP thermal oxidation

The effect of combined gas-phase introduction of vanadium(V) and manganese(IV) oxides on thermal oxidation of InP consists in acceleration of the oxide film formation on the InP samples regardless of the chemostimulators mixture composition. The nonlinear oxide film thickness at the InP surface as a function of the chemostimulators mixture composition has been rationalized as a result of mutual influence of V2O5 and MnO2 changing their heat-induced reactivity and evaporation behavior.

Optical reflectance studies of highly specular anisotropic nanoporous (111) InP membrane

High-precision optical angular reflectance measurements are reported for a specular anisotropic nanoporous (111) InP membrane prepared by doping-assisted wet-electrochemical etching. The membrane surface morphology was investigated using scanning electron microscope imaging and revealed a quasi-uniform and self-organized nanoporous network consisting of semiconductor ‘islands’ in the sub-wavelength regime. The optical response of the nanoporous InP surface was studied at 405 nm (740 THz; UV), 633 nm (474 THz; VIS) and 1064 nm (282 THz; NIR), and exhibited a retention of basic macro-dielectric properties. Refractive index determinations demonstrate an optical anisotropy for the membrane which is strongly dependent on the wavelength of incident light, and exhibits an interesting inversion (positive anisotropy to negative) between 405 and 633 nm. The inversion of optical anisotropy is attributed to a strongly reduced ‘metallic’ behaviour in the membrane when subject to above-bandgap illumination. For the simplest case of sub-bandgap incident irradiation, the optical properties of the nanoporous InP sample are analysed in terms of an effective refractive index neff and compared to effective media approximations.

A comprehensive study of the magnetic, structural, and transport properties of the III-V ferromagnetic semiconductor InMnP

The manganese induced magnetic, electrical, and structural modification in InMnP epilayers, prepared by Mn ion implantation and pulsed laser annealing, are investigated in the following work. All samples exhibit clear hysteresis loops and strong spin polarization at the Fermi level. The degree of magnetization, the Curie temperature, and the spin polarization depend on the Mn concentration. The bright-field transmission electron micrographs show that InP samples become almost amorphous after Mn implantation but recrystallize after pulsed laser annealing. We did not observe an insulator-metal transition in InMnP up to a Mn concentration of 5 at. %. Instead all InMnP samples show insulating characteristics up to the lowest measured temperature. Magnetoresistance results obtained at low temperatures support the hopping conduction mechanism in InMnP. We find that the Mn impurity band remains detached from the valence band in InMnP up to 5 at. % Mn doping. Our findings indicate that the local environment of Mn ions in InP is similar to GaMnAs, GaMnP, and InMnAs; however, the electrical properties of these Mn implanted III-V compounds are different. This is one of the consequences of the different Mn binding energy in these compounds.

Single-Element Passive Quenching with Active Reset Circuit for Single Photon Avalanche Diodes

A single-element passive quenching with active reset (PQAR) circuit is proposed. Its operation mechanism is studied in theory to show that this single element, based on thyristor, can provide similar function of quenching and reset for the free-running Geiger-mode operation of single photon avalanche diodes (SPADs) as the conventional PQAR circuits, but with significant simplicity. Requirement for the thyristor is identified, and an InP sample was designed, fabricated and characterized. Future work for further demonstration is also discussed.

Silicon interfacial passivation layer chemistry for high-k/InP interfaces.

The interfacial chemistry of thin (1 nm) silicon (Si) interfacial passivation layers (IPLs) deposited on acid-etched and native oxide InP(100) samples prior to atomic layer deposition (ALD) is investigated. The phosphorus oxides are scavenged completely from the acid-etched samples but not completely from the native oxide samples. Aluminum silicate and hafnium silicate are possibly generated upon ALD and following annealing. The thermal stability of a high-k/Si/InP (acid-etched) stack are also studied by in situ annealing to 400 and 500 °C under ultrahigh vacuum, and the aluminum oxide/Si/InP stack is the most thermally stable. An indium out-diffusion to the sample surface is observed through the Si IPL and the high-k dielectric, which may form volatile species and evaporate from the sample surface.