Deep Level Transient Spectra Research Articles

Effects of recombination current on the current–voltage characteristics in metal–InGaAs Schottky diodes

Current transport mechanisms were investigated on metal–InGaAs Schottky diodes in which the metal electrodes were deposited at both room temperature and low temperature. Based on fitting of the current–voltage (I–V) characteristics at different temperatures, it was found that the recombination current in the depletion region caused by the deep defect centers was responsible mainly for the deviations of I–V characteristics from the pure thermionic emission mechanism. This effect became more significant for diodes with lower barrier height, under smaller forward bias and at lower measuring temperature. However, the generation current only had subtle influence on the reverse bias characteristics. A deep defect level located at 0.321 eV below the bottom of the conduction band in the InGaAs material, which was identified by the deep level transient spectra measurements, may act as the recombination–generation deep center. The generation lifetime of this deep center may be much longer than its recombination lifetime, therefore it may more severely affect the forward biased I–V characteristics.

Degradation of commercial high-brightness GaP:N green light emitting diodes

Deep level transient spectra, electroluminescence spectra, and light output versus current were measured on diodes degraded by a current stress. It has been shown that the drop in electroluminescence efficiency can be related to a new deep level formed by recombination enhanced reaction from the electron trap attributed to the nitrogen pair in the phosphorus site with silicon in the nearest gallium site.

Formation and Properties of Copper Silicide Precipitates in Silicon

We report results of a detailed study of structural and electrical properties of copper silicide precipitates in silicon. Using conventional and high-resolution transmission electron microscopy we observe that metastable platelets surrounded by extrinsic stacking faults form upon quenching from high temperatures. By ripening experiments at low temperatures as well as by a variation of cooling rates it is shown how homogeneous copper precipitation merges into the heterogeneous precipitation mode of colony growth. The application of recently developed criteria for the interpretation of deep level transient spectra from extended defects allows to conclude that deep electronic states associated with the precipitates have bandlike character.

Formation and Properties of Copper Silicide Precipitates in Silicon

We report results of a detailed study of structural and electrical properties of copper silicide precipitates in silicon. Using conventional and high-resolution transmission electron microscopy: we observe that metastable platelets surrounded by extrinsic stacking faults form upon quenching from high temperatures. By ripening experiments at low temperatures as well as by a variation of cooling rates it is shown how homogeneous copper precipitation merges into the heterogeneous precipitation mode of colony growth. The application of recently developed criteria for the interpretation of deep level transient spectra from extended defects allows to conclude that deep electronic states associated with the precipitates have bandlike character.

Deep-Level Transient-Spectroscopy for Localized States at Extended Defects in Semiconductors

We prove that for localized states at extended defects the high-temperature sides of deep-level transient spectra can be written as a product of an amplitude function depending on the pulse length and a shape function depending on temperature. By this property localized states can be distinguished experimentally from bandlike states. Simulations of deep level transient spectra for localized and bandlike states using the same density of states function and parameter values illustrate the differences and show the failures of conventional analysis in both cases.

Influence of Electric Field-Enhanced Emission on Deep Level Transient Spectra of Bandlike Extended Defects: NiSi2-Precipitates in Silicon

Influence of Electric Field-Enhanced Emission on Deep Level Transient Spectra of Bandlike Extended Defects: NiSi₂-Precipitates in Silicon

Electrical Properties of the Multilayer Structures Based on Ultrathin Diamond-Like Carbon Films

AbstractThe electrical characteristics of multilayer structures based on amorphous ultrathin diamondlike carbon films were investigated including dynamic and quasi-static current-voltage characteristics, capacitance-voltage characteristics, deep level transient spectra. The effect of illumination and temperature on these characteristics was also investigated. For the multilayer structures composed of lower band gap amorphous carbon layers separated with higher band gap ones, there were observed well-defined regions of negative differential resistance and sharp 20-fold changes in capacitance at definite voltages. Activation energies, capture cross sections, and locations of trapping centers were defined. The effects observed are discussed in terms of trap-assisted tunneling and, also, in terms of resonant tunneling between energy levels in superlattices and charge filling of the quantum wells and trapping centers.

Anomaly in the growth rate of anodic oxide films due to the presence of a ( Sm + Sm2O3) overlayer at a GaAs surface

To our knowledge, no experiments on plasma anodic oxidation of heavily doped GaAs, assisted by very thin samarium overlayers, have been reported up to now. The following interesting results are obtained from the investigation of a Sm-based oxide/GaAs structure: (i) a rapid increase of the oxide growth rate; (ii) a possibility of important changes of the electronic properties of the interface, especially suppression of the high-temperature part of the charge deep level transient spectra; (iii) an appreciable distortion of the subsurface bulk crystal lattice of the anodized semiconductor. A sketch of the oxide growth mechanism is presented. We have attempted to prove that before the oxidation process itself the Ga and As atoms diffuse into the ( Sm + Sm 2 O 3) overlayer and a rare-earth compound is formed.

Characterization of deep levels and carrier compensation created by proton irradiation in undoped GaAs

Deep levels and carrier compensation created in undoped metal-organic chemical-vapor deposition grown GaAs by low fluence proton irradiation (1×108−1×1010 cm−2) are investigated by the deep level transient spectroscopy technique and capacitance-voltage profiling. At least five main electron traps are observed after room-temperature irradiation in addition to the EL2 present in the as-grown material. Irradiation generates additional EL2, which annihilate at much lower temperatures than one would expect for isolated EL2. However, with further increase in irradiation fluence, the magnitude for this additional increment begin to decrease. The apparent decrease in the EL2 peak is accompanied by an increase of a broad peak in the deep level transient spectroscopic spectrum. This broad peak has a highly nonexponential capacitance transient and it is suggested to result from the interaction of the additional EL2 with EL6. One of the observed traps, with energy level, (Ec−0.40) eV, has not previously been reported in proton irradiated GaAs. The signature of this trap resembles that of EL5 and is quite stable at moderate annealing temperatures; annihilating completely only at a temperature of ∼600 °C. This level shows a saturation effect with increasing irradiation dose and we believe it is related to complex defect-impurity formation. The temperature dependence of the carrier profiles reveals some complex behavior of carrier compensation, including acceptor- and donor-like properties of the various traps.

Peak and side data analyses to measure deep levels by DLS-82E lock-in spectrometer

An analysis utilizing the low and high temperature side data of deep level transient spectra for the DLS-82E lock-in spectrometer is described. A bulk center in metal-insulator-InP structure has been examined by the DLS-82E spectrometer to demonstrate the practical application of the proposed procedure. The analyses utilizing both the peak and side data of deep level transient spectroscopy spectra were carried out and the obtained results were discussed.

Deep level transient spectroscopy investigation of GaAs grown by atomic layer molecular beam epitaxy

We report on deep level incorporation in GaAs grown by atomic layer molecular beam epitaxy (ALMBE). In contrast to the case of MBE GaAs, where the main features of the deep level transient spectra strongly depend on the growth temperature T S for 370⩽T S ⩽530 ° C , GaAs grown by ALMBE shows only three peaks, which correspond to the M1, M3 and M4 levels typical of MBE GaAs, together with a fourth trap, that we label M(330). The concentrations of these levels are comparable with those measured in MBE GaAs grown at 600°C and are weakly dependent on T S , in any case being smaller than 1.7×10 13 cm −3 ; these values are up to three orders of magnitude lower than those observed in MBE GaAs grown at comparable temperatures. Thus, as far as deep levels are concerned, ALMBE GaAs grown at 370⩽T S ⩽450° C can be compared with GaAs grown MBE at conventional temperatures (about 600°C).

On the influence of an ultrathin Al overlayer on GaAs plasma oxide growth kinetics

The growth rate of GaAs anodic oxide in radio-frequency plasma at low temperatures can be strongly affected by an ultrathin aluminum layer (<3 nm) evaporated on the semiconductor before oxidation. The effect of this layer on the properties of the resulting oxide-GaAs interface has been investigated. Comparing the structures grown by means of the Al overlayer to the sample with a pure native oxide, the corresponding deep level transient spectra differ markedly and the GaAs lattice contraction below the double oxide is reduced. Application of a fitting procedure to a simple layer growth model leads to interpretation of the investigated process by increasing both the migration coefficient of the negative oxygen ions in the oxide and concentration of O - ions on the dielectric surface during the oxidation procedure.

Effect of dislocation loop size on the deep level transient spectrum in Si

Effect of dislocation loop size on the deep level transient spectrum in Si

Light-beam-induced transient spectroscopy of oxidation-induced stacking faults in silicon

Abstract We have applied the technique of light-beam-induced transient spectroscopy, which characterizes minority carrier capture and emission at point and extended defects, to oxidation-induced stacking faults in n-type silicon. We have compared the minority carrier trap data with conventional deep-level transient spectra for majority carrier traps. We find that we are able to distinguish between hole capture at randomly distributed point defects (e.g Au), and hole capture at point defects which are associated with the extended-defect strain field.

Electrical characteristic frequency dispersion of diamond polycrystalline films

The electrical characteristics of thick diamond polycrystalline films grown on metal substrates by the method of chemical crystallization from the electrically activated gas phase were investigated. The active and reactive components of the complex conductivity of the films were measured as functions of the frequency and temperature in the ranges 10-10 5 Hz and 80–900 K respectively. For the first time, charge-based deep-level transient spectra of insulating diamond films were also obtained using rate window scanning. From the analysis of the experimental results, three carrier transport mechanisms were concluded to be possible, each of them being dominant in different temperature ranges; the grain-boundary-barrier-limited currents at high temperatures, the conductivity along the disordered intercrystallite boundaries through the allowed band tails at intermediate temperatures, and jumping conductivity between localized states of the intercrystallite boundaries near the Fermi level at low temperatures. The parameters of trapping centres were determined. The dependences of the integral density of the recharging trap centres, and the frequency and temperature dispersions of the electrical characteristics were determined as functions of the CH 4 concentration in the gas mixture during the diamond film crystallization.

Light Induced Rapid Thermal Diffusion of Boron Atom in Silicon

We have studied the light induced rapid thermal diffusion of boron atom in silicon. The samples were heated by the rapid thermal processor. We have carried out spreading resistance and deep level transient spectroscopy (DLTS) measurements. The impurity distribution profile is much shallower and steeper than that of conventional thermal diffusion and the diffusion depth can be controlled to 0.1 μm. Several peaks in the deep level transient spectra were detected and the density of these defects ranges from 0.5×1012 to 5.6×1012 /cm3. The passivation and annihilation of these defects have been studied. We have also made the planar diode whose diameter is 500 μm. The reverse current and the back breakdown voltage of the planar diode are 10-9 A and 80 V respectively.

Nonexponential deep level transient spectroscopy analysis of moderately doped bulk n-GaAs

A theoretical analysis is carried out of deep level transient spectra (DLTS) obtained on bulk moderately doped n-GaAs. The semiconductor is considered as a disordered one because fluctuations in the concentration of shallow donors and acceptors produce a random potential energy with a root-mean-square (RMS) fluctuation comparable to the mean thermal energy of the electrons. As a result, the energies of the deep levels obey a Gaussian distribution of the same RMS deviation. An original algorithm for the computer simulation of DLTS spectra is presented. The corrections to the peak energy and concentration of deep levels due to the random potential are estimated. Useful theoretical information about the microscopic parameters of the disordered system is presented as well. The degree of compensation of the material is determined.

Disorder-induced band-tailing effects on deep levels in semiconductors

We have investigated the effects of disorder-induced band tailing on deep levels in compound semiconducting alloys, such as GaAs and AlxGa1−xAs. In particular, we have eliminated the assumption of Gaussian broadening of the defect density of states proposed earlier by others on the basis of the central-limit theorem. The expressions derived for the transient capacitance in the presence of the disorder-induced band tailing are quite different from previously published results and indicate that the form of the broadening function is quite sensitive to, and should closely reflect, the underlying physical environment. We applied this theory to the investigation of the deep-level transient spectra (DLTS) and isothermal capacitance transient spectra (ICTS) in GaAs and AlxGa1−xAs. Our results indicate that standard experimental measurements with DLTS and ICTS, in general, can underestimate the activation energy, capture cross section, etc., even in the case of weak disorder.

Identifications of photoluminescence and deep level transient spectra for Te-doped AlxGa1-xAs

A bound-exciton and a donor-acceptor (D-A) pair emission in photoluminescence are identified for Te-doped AlxGa1-xAs. The D-A pair emission near band edge is assigned as Te-related donor to carbon acceptor transition and the donor binding energy is determined as a function of composition x up to 0.75. Except the deep DX level, a new shallower deep state is found in deep level transient spectra under light illumination and is associated with Te-related donor state in PL.

Deep-level transient spectroscopy of AlGaAs and CuInSe2

Abstract A new technique is used to obtain the activation energies and capture cross-sections of closely spaced traps. It is applied to single-crystal p-type CuInSe2 prepared by the vertical Bridgeman method and selenium-doped Al x Ga 1−x As (x = 0.27) grown by metal-organic chemical vapor deposition. Deep centers, which are active in the same temperature range, usually yield overlapping peaks in conventional deep-level transient spectroscopy rate-window spectra. The digitally recorded capacitive transients are analyzed directly by fitting a double exponential to the data. This fitting produces two Arrhenius plots which yield the trap depths of the two defects. This technique revealed two hole traps for CuInSe2 at 423 and 489 meV. Likewise, for AlGaAs, electron traps were discovered at 435, 455 and 368 meV. The first two energy levels were obtained by applying the double exponential fit in the temperature range 214–246 K. The energy level of the third state was the result of a single exponential fitting in the temperature range from 184 to 214 K after subtracting the two known traps from the transient. It will also be shown that the agreement between the new technique and the standard technique is excellent, and considerably more information about the traps is obtained.