DLTS Study Research Articles

DLTS studies of defects produced in n-type silicon by hydrogen implantation at low temperature

ABSTRACTMetastable defects are discovered in hydrogen-implanted n-type silicon. Hydrogen implantation was performed with the energy of 80 keV to a dose of 2×10 cm- at 109 K. After implantation, the sample temperature was raised to room temperature. DLTS measurements were carried out in the temperature range 80–290 K for fabricated diodes. When the sample is reverse-biased at 10V for 10 min at room temperature and then is cooled down to 80 K, three new peaks labeled EM1, EM2 and EM3 appear around 150, 190 and 240 K, respectively. The introduction of metastable defects is found to be characteristic of low temperature implantation. We have evaluated properties of EM1 in detail. EM1 with thermal emission activation energy of 0.29 eV has a peak in concentration around the depth of 0.64 μ m, which corresponds to the projected range of 80 keV hydrogen. EM1 is regenerated with the reverse bias applied around 270 K and is removed with the zero bias around 220 K.

Illumination effects in irradiated 6H n-type SiC observed by positron annihilation spectroscopy

In the present study, we used positron annihilation spectroscopy to investigate defects after electron irradiation in 6H n-type SiC. The density of vacancy-type defects strongly increased during this treatment. An isochronal annealing experiment was performed, and the main recovery stage was found to be between 1000°C and 1400°C. This corresponds to the annealing range of the E 1/E 2 defect, which was also found by a correlated positron and DLTS study in 6H–SiC epilayers after electron irradiation (J. Appl. Phys. 80 (1996) 5639). Optical excitation experiments during the positron experiment show that the observed defect has an ionization level at about E c−0.47 eV, which is similar to the level E c−0.44 eV obtained by DLTS for the E 1/E 2 defect (Appl. Phys. Lett. 74 (1999) 839). Doppler-coincidence experiments suggest that the observed vacancy is surrounded by C atoms, so that most probably the Si vacancy (isolated or bound to an impurity or another defect) is the dominating defect after electron irradiation.

High resolution Laplace DLTS studies of defects in ion-implanted silicon

We have used high resolution Laplace deep level transient spectroscopy (LDLTS) to investigate defects in n-type silicon caused by implantation of Si, Ge or Er with doses of the order of 1×10 9 cm −2 . These are compared with defects created in proton irradiated n-type silicon. Unlike the simple proton irradiated case, LDLTS spectra of ion implanted silicon show that there are many emission rates associated with defects with energies in the region of E c−400 meV. We have carried out annealing studies and Laplace DLTS depth profiling and show that the complex spectra measured from a region less than half way through the implant simplify as the profile is moved through the implant and towards the tail. Annealing studies show that these defects survive an anneal that should remove the E-centre.

DX centers in indium-doped Cd0.9Mn0.1Te

Abstract Deep levels in indium-doped Cd0.9Mn0.1Te material were studied by DLTS, thermally stimulated capacitance (TSC) and photocapacitance measurements. The persistent photoeffects observed at low temperature indicate existence of metastable centers in the material. One of the trap related to metastable defects has been identified: the level with activation energy obtained from DLTS studies equal to 0.22 eV, a very high concentration of the associated traps (higher than 10% of the concentration of the shallow levels) and energy barrier for capture equal to 0.1 eV. Stokes shift for this level has been found to be equal to 0.58 eV.

GROWTH AND CHARACTERIZATION OF GaAs BY METALORGANIC CHEMICAL VAPOR DEPOSITION USING TRIETHYLGALLIUM AND SOLID ARSENIC

GaAs-low compensated layers were grown by using an atmospheric MOCVD system. Solid arsenic and triethylgallium (TEG) were used as precursors. The layers exhibit an electron mobility greater than 30,000 cm2/V-sec at 77K for best growing conditions. This is the highest value reported until now for MOCVD GaAs grown by using non-arsine based alternative arsenic sources. The resulting layers were n-type with a minimum electron concentration of 1015 cm-3. The DLTS studies shown the EL2 electron level as the dominant trap with a concentration of 1013 cm-3.

DLTS study of deep levels in GRIN–SCH–SQW GaAs/AlGaAs laser diode structures grown by MBE

Abstract Deep level transient spectroscopy has been used to measure the electrical activity of deep levels present in graded refractive index separate confinement heterostructure single quantum well laser diodes grown by molecular beam epitaxy. We report the use of untypical sequences of filling pulses to show that the main minority trap at ΔE B =0.78 eV acts as an effective non-radiative recombination center. Changes observed in the trap concentration, depending on growth conditions of the structures, can be a reason why photoluminescence intensities measured in the structures increase for higher substrate temperature and are in excellent correlation with threshold currents of lasers made of the structures.

Drain-current DLTS study of an GaAs/InP MESFET

Fast GaAs Metal–Semiconductor Field-Effect-Transistor (MESFET) on InP exhibiting promising performances comparable to those grown on GaAs subtrates have already been fabricated. The lattice mismatch of 4% between GaAs and InP did not preclude device fabrication, although the characterization of such materials has shown the existence of high dislocation density at the interface and a residual biaxial tensile strain due to the difference between the thermoelastic properties of the two materials. The above-mentioned growth difficulties can generate many defects, which are very detrimental for device application. In this context, we have investigated deep levels on Rapid Thermal Annealed (RTA) GaAs/InP MESFET by means of Drain-Current Deep-Level Transient Spectroscopy (CDLTS). In this study, we have revealed the absence of dislocation-generated-deep level, the formation of an apparent “hole-like” observed for the first time with an activation energy of 0.3eV. On comparison with homo-epitaxial GaAs MESFET achieved under the same conditions, we note the absence of a deep level with an apparent activation energy of 0.4eV.

DLTS study of nucleation stage of oxygen precipitate in silicon

Oxygen precipitate formation at 600–700°C was studied by a new method based on DLTS data analysis. OP formation goes on through the creation of oxygen-rich local areas in the silicon matrix. The accumulation of oxygen atoms in these areas with annealing time leads to the phase transformation starting with some critical oxygen concentration. OP nuclei has a friable structure with a high surface-to-volume ratio.

Conductance deep-level transient spectroscopic study of anomalous hole trap in GaAs MESFETs

The anomalous `hole' trap like peaks observed in conductance DLTS spectra of GaAs MESFETs have been previously studied and have been associated with surface states present in the ungated regions at the GaAs-passivant interface. Besides these peaks, the conductance DLTS study of thermal emission and capture by these interface traps also indicates the presence of an associated surface conducting layer. These results show that electrons from this thin conducting layer interact with the interface states giving rise to a temperature-dependent surface leakage current when the Schottky gate is reverse biased with respect to the source and/or drain. This surface current affects both the capture and the emission processes of the interface traps. From the conductance DLTS measurements on GaAs MESFETs passivated with films, we have extracted a characteristic thermal activation energy of 0.43 eV for the interface electron traps, in both of these modes. A two-dimensional interface state band model has been used to explain our experimental results reported in this work.

DLTS study of oxygen precipitates in silicon annealed at high pressure

The evolution of oxygen precipitates (OPs) created at 900–1000 K in SiCz with initial oxygen concentration 8 × 10 17 cm −3 was studied by DLTS technique. The samples were subjected to high pressure (HP) treatment up to 1.3 GPa at high temperature (HT, 1230–1550 K) which caused a partial dissolution of OP. A new way of studying the oxygen distribution is suggested. It is based on the investigation of an electrically active complex of the oxygen atom with a vacancy (A-center, level E c − 0.18 eV). A-centers were introduced by 3.0 MeV electron irradiation with dose 1 × 10 15 cm −2 and DLTS was used for A-center agglomerates detection. The analysis of data obtained allows one to conclude that the irradiation dose used does not decompose OPs. It has been found that hydrostatic pressure retards OP dissolution at HT treatment through a decrease in the migration energy E a, coefficient D o and diffusion coefficient D. The effect is explained on the assumption that oxygen diffuses in the form of connected pairs of the oxygen and self-interstitials.

DLTS study of GaAs MIS structures with plasma deposited insulator

The results of a DLTS study of GaAs MIS structures with plasma deposited Si3N4 as insulator are given. It is established that the activation energy and the capture cross section of traps decrease with reverse bias and at large biases correspond to the respective parameters of bulk traps. A correlation is found between the DLTS spectra and the maximum HF capacitance of the MIS structure in the “accumulation” region. Experimental data are explained in the framework of a “unified defect model” by the change of the potential relief in a semiconductor as a result of a high-resistivity layer formed near the interface. The interpretation of the DLTS spectra of the GaAs MIS structures is discussed. [Russian Text Ignored].

DLTS study of deep traps in Si varactor structures

DLTS study of deep traps in Si varactor structures

DLTS Study on Annealed Low-Temperature GaAs Layers with An n-I(LT)-n Structure Grown by MBE

AbstractDeep levels in the annealed low-temperature molecular beam epitaxial (LT-MBE) GaAs layer were successfully characterized by using the capacitance deep-level transient spectroscopy (C-DLTS) as well as photocapacitance quenching technique in combination with a unique sample structure. In this work, we have fabricated the samples by inserting the LT-GaAs layer into two n-type semi-conductive layers, like a sandwich (n-LT-n structure), grown at normal substrate temperatures. DLTS measurements have revealed that one electron trap dominates the annealed LT-MBE GaAs. The dominant electron trap was very similar to the so-called EL3 level. Moreover, we found the midgap level appeared upon 800-900°C RTA, although no midgap level was detected in the as-grown n-LT-n sample (annealed at 620°C) and confirmed with photoquenching measurements that it is the EL2 level.

Thermal cycling, DLTS, and PEC studies on LEC gallium arsenide

AbstractThis paper discusses the growth of gallium arsenide single crystals using the LEC technique. The Semi‐insulating gallium arsenide was studied. The defect investigations were made by DLTS and etching studies. The variation of deep level concentration along the wafer was estimated using DLTS. The fabrication and efficiency of the PEC Solar cells are also reported.

DLTS Studies of Thermally Treated Carbon-Rich Silicon

DLTS Studies of Thermally Treated Carbon-Rich Silicon

Generation of the EL2 defect in n-GaAs irradiated by high energy protons

Presents the results of the DLTS study of irradiation-induced defects in n-GaAs irradiated by 6.7 MeV protons at T=300 K. It has been found that the irradiation produces the EL2 defect showing the persistent photoquenching (PPQ) effect. With increasing irradiation dose Phi p>or=1*1011 cm-2 the concentration of irradiation-induced defects grows and their interaction becomes stronger. This changes the electrical properties of the EL2 defect: the thermal activation energy and the charge carrier cross section change. The experimental data permit the EL2 to be identified as the isolated antisite defect AsGa.

DLTS Study of Electron Traps in Polycrystalline n-CdTe

physica status solidi (a)Volume 132, Issue 1 p. K39-K41 Short Note DLTS Study of Electron Traps in Polycrystalline n-CdTe V. Bikbaev, V. Bikbaev Department of Semiconductor Physics, Vilnius University Search for more papers by this authorP. Pranaitis, P. Pranaitis Department of Semiconductor Physics, Vilnius University Search for more papers by this authorS. Singh, S. Singh Department of Physics, G. B. Pant University of Agriculture and Technology, Pantnagar Search for more papers by this authorJ. Vaitkus, J. Vaitkus Department of Semiconductor Physics, Vilnius University Search for more papers by this author V. Bikbaev, V. Bikbaev Department of Semiconductor Physics, Vilnius University Search for more papers by this authorP. Pranaitis, P. Pranaitis Department of Semiconductor Physics, Vilnius University Search for more papers by this authorS. Singh, S. Singh Department of Physics, G. B. Pant University of Agriculture and Technology, Pantnagar Search for more papers by this authorJ. Vaitkus, J. Vaitkus Department of Semiconductor Physics, Vilnius University Search for more papers by this author First published: 16 July 1992 https://doi.org/10.1002/pssa.2211320134Citations: 1 Building 3, Saulétekio al. 9, 2054 Vilnius, Lithuania. Pantnagar 263145, India. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume132, Issue116 July 1992Pages K39-K41 RelatedInformation

Electronic levels and properties of the selfinterstitials in irradiated silicon

DLTS studies of the electronic states and properties of irradiated p-type silicon are performed. The injection-enhanced annealing is observed for two traps E2( E c−0.39 eV) and E1( E c−0.26 eV). The annealing of E2 and E1 are simulataneous with the growth of the hole traps connected with V, C i and Al i. It is concluded that the observed electronic levels belong to the different charge states of silicon selfinterstitial E2=Si i +3s 23p)/Si i 2+(3s 2) and E1=Si i 0(3s 23p 2)/Si i +(3s 23p). The conclusion is confirmed by the differences of the cross-sections of the formation of Al i and C i as well as by the influenceof the zero and reverse bias conditions on the introduction rate and optical annealing of the E2 state.

DLTS studies of low-t emperature annealing in lithium-d oped silicon

DLTS studies of annealing kinetics are carried out for 1 MeV electron irradiated lithium-d oped silicon p-n solar cells. The results obtained show that during low-t emperature annealing Li atoms actively interact with radiation defects, transforming them into complexes with low recombination properties. New deep levels (Ec−0.36 eV) and (Ev0.30 eV), associated with lithium-c ontaining complexes are observed. A multistage annealing model for annealing of radiation defects is proposed. An explanation of the annealing kinetics as well as the identification of the new deep levels is given on the base of the model. [Russian text ignored]

The DLTS Study of Perovskite Oxides LnMO<sub>3+δ</sub>(Ln=Nd, Sm, Eu, M=Mn, Co) as Gas Sensor Materials

The DLTS Study of Perovskite Oxides LnMO<sub>3+δ</sub>(Ln=Nd, Sm, Eu, M=Mn, Co) as Gas Sensor Materials