N-type InP Research Articles

Electrochemical Functionalization of InP Porous Nanostructures with a GOD Membrane for Amperometric Glucose Sensors

The electrochemical functionalization of n-type InP porous nanostructures and their feasibility for biochemical sensor applications were investigated. The porous structures have extremely large surface areas, i.e., over , and superior electrical properties with conductive semiconductor substrates. As a first attempt at electrochemical functionalization, we successfully deposited a glucose oxidase (GOD) membrane onto an InP surface under an applied anodic bias of 1.2 V. With the addition of glucose, the response currents on the porous electrodes increased compared to those on planar InP electrodes due to their enlarged surface area. The sensitivity curves of the porous electrodes we used showed good linearity between the response currents and concentrations in a range from 0 to 5 mM.

Electrophoresis deposition of metal nanoparticles with reverse micelles onto InP

Abstract Nanolayers were deposited onto surfaces of n-type InP single crystal wafers by electrophoresis from reverse micelle colloid solutions containing palladium nanoparticles. Two types of nanolayers were deposited, by applying a positive potential or a negative potential on the InP wafer. Further, wafers with nanolayers were annealed in high vacuum at 400 °C. The nanolayers were studied using capacitance–voltage characteristics on a mercury probe, by atomic force microscopy and by secondary-ion mass spectroscopy. Two types of Schottky-like diodes were prepared on wafers with the two types of nanolayers and studied by current–voltage characteristics. The diodes with nanolayers deposited by applying the positive potential, which contained Pd nanolayers, showed characteristics with better rectifying properties than the other type of diodes. Correlations among measured characterizations were found.

Simulating Crystallographic Pore Growth on III-V Semiconductors

In this work, the growth of crystallographically oriented pores in III-V semiconductors has been investigated. Based on new and previous results a model for pore growth has been developed, which is mainly based on a stochastic branching probability of the pores. The stochastic nature of the model allowed to implement it as the core for Monte-Carlo-Simulations of pore growth. The simulations were able to reproduce the main features of crystallographically oriented pores, like uniform pore growth in n-type InP or the formation of domains on n-type GaAs and InP. The model is also capable of reproducing the logarithmic growth law for the pore depth, as well as the pore density oscillations with depth, as recently found.

Growth Mode Transition of Crysto and Curro Pores in III-V Semiconductors

The formation of crystallographically oriented and current line oriented pores in n-type InP is reviewed and compared to other semiconductors in the light of some new results. A model for the formation of crystallographically oriented pores is presented that reproduced salient features of this pore type rather well. Impedance data together with their model-based evaluation are given and discussed. Some self-organization features of current line oriented pores and their possible relation to self-induced or externally triggered growth mode transitions between the two pore types conclude the paper.

Investigation on deep level defects in rapid thermal annealed undoped n-type InP

Deep levels in rapid thermal annealed Pd/n-InP Schottky contacts have been studied using deep level transient spectroscopy. It is observed that the as-deposited Pd/n-InP Schottky sample exhibit two deep levels with activation energies of 0.53 and 0.70 eV. In samples annealed at 400 °C, three deep levels having activation energies 0.18, 0.30 and 0.86 eV below the conduction band are observed and for samples annealed at 500 °C, four deep levels with activation energies 0.33, 0.44, 0.70 and 0.82 eV are observed. Fourier transform infrared spectroscopy measurements have been carried out on undoped as-deposited and annealed InP wafers at 300, 400 and 500 °C. The measurements revealed high concentration of hydrogen complexes in the form of VInH4 existing in InP wafer. The results show that VInH4 complex annihilates with increase of annealing temperature and results in the formation of P In 2+ and V P + defects at 0.70 and 0.44 eV, respectively.

Fabrication of microstructures in III–V semiconductors by proton beam writing

While the creation of microstructures in Si and GaAs by irradiation with high energy protons and helium ions and subsequent electrochemical etching has already been reported, the creation of microstructures in InP using this technique is investigated here for the first time. It is demonstrated that proton irradiation of Fe-doped semi-insulating InP(0 0 1) leads to an amplified material removal in the irradiated areas during electrochemical etching in an HF solution. By this way microstructures were produced using a 2.25 MeV proton beam focused down to ∼1 μm. The depth of the etched structures depends on the etching procedure. In addition, amplified etching of non-irradiated material encircled by closed irradiated patterns was observed. Furthermore, irradiation with helium ions leads to the formation of thin freestanding InP layers by simultaneous underetching as well as etching from the sample surface of the irradiated regions. In contrast to the semi-insulating material, the irradiation and electrochemical etching of n-type InP results in an amplified formation of porous material which partly leads to a complete removal of the material in the irradiated areas. A comparison between GaAs and InP concerning the dissolution characteristics shows mainly a similar behavior of the semi-insulating types of these semiconductors and of the n-type materials.

Current-Voltage Measurements on Indium Phosphide Schottky Diodes

In this paper, current-voltage (i-Vg) results from different kinds of n-type InP Schottky diodes are reported. The diodes were fabricated on an unintentionally doped n-type (100) indium phosphide substrate, and the i-Vg characteristics were measured in the temperature range 100 300 K. For the ideality factor, n always exhibited a small (1) but continuous increase with the voltage. At higher forward voltage, slightly higher values of n were due to series resistance effect; in other words, the interface state density always remained small. However, it was possible to obtain some information in the case of discrete interface traps. It was shown that i-Vg measurements can be used as a fast method to determine the densities of the interface states when they equilibrate with the semiconductor.

Rapid thermal annealing effects on electrical and structural properties of Pd/Au Schottky contacts to n-type InP(111)

The effects of rapid thermal annealing on the electrical and structural properties of Pd/Au Schottky contacts to n-type InP(111) have been investigated by current–voltage (I –V), capacitance–voltage (C –V) and X-ray diffraction (XRD) measurements. The barrier height of the as-deposited Pd/Au Schottky contact was found to be 0.46 eV (I –V) and 0.70 eV (C –V) respectively. It is observed that the Schottky barrier height increases with annealing temperature and found maximum values of 0.51 eV (I –V) and 0.92 eV (C –V) annealed at 400 °C for 1 min in the nitrogen atmosphere. However, after annealing the sample at 500 °C resulted in the decrease of barrier height and values are 0.40 eV (I –V) and 0.60 eV (C –V). The AFM results showed that the surface morphology of the contact annealed at 500 °C is fairly smooth with a RMS roughness 1.9 nm. Based on the XRD results, the formation of indium phases at the Pd/Au/n-InP interface could be the reason for the increase in the Schottky barrier height at 400 °C. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Single-cycle azimuthal angle dependence of terahertz radiation from (100) n-type InP

We have observed that the terahertz power emitted by (100) n-type InP exhibits a single maximum and a single minimum as the crystal is rotated through 360° about its surface normal. This stands in contrast to other semiconductor terahertz emitters for which two, three, or four maxima per rotation have been observed. We have investigated the terahertz emission as a function of sample doping, optical excitation fluence, and applied in-plane magnetic field. The data cannot be accounted for by bulk optical rectification. We suggest that the origin of the phenomenon may be related to crystal twinning.

Anodic etching of InP using neutral NaCl electrolyte

We present porous InP formation in neutral NaCl solution. N-type InP wafers were etched at linear sweep voltammetry and at constant potential, respectively. The results showed that the potential 7.0–8.5 V is suitable for forming the regular pores of InP. The reaction that the eight holes are used to dissolve one InP molecule was confirmed by our experimental results. The crystallographically oriented pores of InP formed were suggested to be the synergic effect between surface state and effect of the surface curvature. The current-line oriented pores formed were ascribed to the effect of surface curvature.

Self-assembly structure formation on patterned InP surfaces

Self-assembly of polystyrene spheres guided by patterned n-type InP substrates has been investigated. InP surfaces were patterned using a variety of methods including wet chemical etching, sputter coating, thermal evaporation, and photo lithography. The self-assembly of polystyrene spheres depended on the appearance of patterns and was affected by the deposition techniques (sputter coating and thermal evaporation) of Au micro-squares. SEM and AFM were used to characterize the surface morphologies.

Blueshift of electroluminescence from single n-InP nanowire/p-Si heterojunctions due tothe Burstein–Moss effect

Single-crystalline n-type InP nanowires (NWs) with different electronconcentrations were synthesized on Si substrates via the vapor phase transportmethod. The electrical properties of the InP nanowires were investigated byfabricating and measuring single NW field-effect transistors (FETs). Single InPNW/p+-Si heterojunctions were fabricated, and electroluminescence (EL) spectra fromthem were studied. It was found that both the photoluminescence (PL) spectraof the InP NWs and the EL spectra of the heterojunctions blueshift from 920to 775 nm when the electron concentrations of the InP NWs increase from2 × 1017 to1.4 × 1019 cm−3. The blueshifts can be attributed to the Burstein–Moss effect rather than thequantum confinement effect in the InP NWs. The large blueshifts observed in thisstudy indicate a potential application of InP NWs in nano-multicolour displays.

In-Situ FFT Impedance Spectroscopy during the Growth of n-type InP "Crysto Pores"

In this work the growth of crystallographically oriented pores in n type InP is studied. The evolution of the pore structure with time is outlined in detail. It is found that growth and branching of these pores in different crystallographic directions depend on the etching time. Besides an ex-situ evaluation of the pore structure by micros-copy, in-situ FFT impedance spectroscopy measurements have been performed. A model has been found which fits the data consistently. First steps towards a physico-chemical understanding of the processes underlying the pore growth have been made, yielding a qualitative view of pore growth.

Highly Stable 1.3-$\mu\hbox{m}$ -Wavelength Lasers With p- and n-InP Buried Heterostructure

Highly stable 1.3-mum-wavelength Fabry-Perot lasers with a p- and n-type InP buried heterostructure have been achieved at an ambient temperature of 85 degC. The t 0.5 deterioration (second-stage degradation) property does not appear clearly within 6000 h, and the saturated first-stage degradation property remains. It is confirmed that the fabricated 1.3-mum FP lasers have a different optical-beam-induced-current characteristic from lasers suffering from t 0.5 deterioration. The first-stage degradation is due to the deterioration of the active layer and is attributed to the fact that some nonradiative recombination centers are generated in the active layer.

Crossover phenomenon for variable range hopping conduction and positive magnetoresistance in insulating N-Type InP

Crossover phenomenon for variable range hopping conduction and positive magnetoresistance in insulating N-Type InP

Crossover phenomenon for variable range hopping conduction and positive magnetoresistance in insulating N-Type InP

Dans ce travail, nous avons utilise le phenomene de la magnetoresistance pour expliquer le passage du regime de conduction par saut a distance variable de Mott vers celui d'E-S dans un echantillon isolant d'InP. En effet nous avons observe sur cet echantillon une magnetoresistance positive accompagne d'un regime de conduction par saut a distance variable a tres basses temperatures et en presence du champ magnetique. Les resultats experimentaux ont ete compare a des modeles theoriques adequats pour apporter une explication physique aux phenomenes observes.

Control of Zn diffusion in InP/InAlGaAs-based heterojunction bipolar transistors and light emitting transistors

Zn diffusion behavior in InP/InAlGaAs heterojunction bipolar transistors and light emitting transistors grown by metalorganic chemical vapor deposition was investigated. Using secondary ion mass spectrometry, the Zn doping profiles in the epitaxial structures were studied in relation to their growth conditions. Migration of Zn atoms from the base layer was found to be a combined result of three mechanisms, i.e. the generation of excess group III interstitials during the n-type InP subcollector growth, the generation of Zn interstitials in the Zn-doped InAlGaAs base, and the presence of strong electric field at the emitter-base n–p junction. By choosing the growth conditions either to suppress or to enhance the effects of each mechanism, Zn is able to diffuse either in both directions into the adjacent emitter and collector, or forward only into the emitter, or backward only into the collector. An abrupt junction profile, with the suppression of Zn diffusion, in the InP:Si/In(Al 0.25Ga 0.75)As:Zn/InAlAs:ud/InP:Si light emitting transistor structure has been achieved by low Si doping in the InP subcollector, low temperature growth of the InAlGaAs base, and slightly high Si doping in the InP emitter.

Temperature-dependent current–voltage and capacitance–voltage characteristics of the Ag/n-InP/In Schottky diodes

The current–voltage (I–V) and capacitance–voltage (C–V) characteristics of Ag/n-InP/In Schottky diodes have been studied in a wide temperature range by steps of 10 K. A decrease in the apparent barrier height (BH), \(\Upphi_{bo}\), an increase in the ideality factor, \(n\) and a nonlinearity in the activation energy plot with a decrease in temperature have been seen. The experimental values of BH and ideality factor for the devices were calculated as 0.61 eV and 1.18 at 320 K, 0.48 eV and 1.52 at 200 K, and 0.20 eV and 3.89 at 70 K, respectively. An abnormal decrease in the experimental BH \(\Upphi_{b}\) and an increase in the ideality factor n with a decrease in temperature have been explained by the barrier inhomogeneities at the metal–semiconductor (MS) interface. From the temperature dependent I–V characteristics of the Ag/n-InP contact, that is, \(\overline{\Upphi}_{bo}\) and A* as 0.79 and 0.55 eV, and 7.96 and \(8.18\,\hbox{A/cm}^{2}\hbox{K}^{2}\), respectively, have been calculated from a modified \(\hbox{ln}(I_{0}/T^{2})-q^{2}\sigma _s^2/2k^{2}T^{2}\) vs. 1/T plot for the two temperature regions. The Richardson constant values are in close agreement with the value of \(9.8\,\hbox{A/cm}^{2}\hbox{K}^{2}\) known for n-type InP. Moreover, the difference between the apparent BHs obtained from the I–V and C–V characteristics has been attributed to the existence of Schottky BH inhomogeneity.

Degradation Analysis of 2-$\mu\hbox{m}$ DFB Laser Using Optical Beam-Induced Current Technique

The degradation behavior of 2-mum wavelength distributed feedback lasers with a p- and n-type InP buried heterostructure during constant-power aging is investigated. The degradation mechanism is governed by diffused defects with a parallel direction in the crystal plane. Furthermore, it is clarified that the epitaxial layers on the mesa affect both first- and second-stage degradations.

Four-point probe electrical measurements on p-n-p InP structures

The diffusion of zinc into n-type InP has been studied by four-point probe electrical measurements on homogeneously doped crystals at 750 ºC. The zinc carrier concentration in the diffused layer was approximately 3 x 10(18) cm-3 and its mobility was assumed to be about 40 cm² V-1 s-1. It was observed that the concentration of free carriers throughout the entire diffused region is always less than the number of introduced impurity atoms. Possible reasons are discussed to explain the observed differences. Moreover this non-correlation phenomenon did provide substantial backing to the Hall Effect and C-V measurements that are being carried out to further analyse the Zn-InP diffused layer.