Characterization Of Deep Level Defects Research Articles

Characterization of deep-level defects in highly-doped silicon with asymmetric structure by transient capacitance spectroscopy

Characterization of deep-level defects in highly-doped silicon with asymmetric structure by transient capacitance spectroscopy

Characterization of deep-level defects in GaNAs/GaAs heterostructures grown by APMOVPE

AbstractConventional deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS techniques were used to study electrical properties of deep-level defects in dilute GaNAs epitaxial layers grown by atmospheric-pressure metalorganic vapourphase epitaxy (APMOVPE) on the GaAs substrate. Three samples with nitrogen concentrations of 1.2 %, 1.6 % and 2.7 % were investigated. In DLTS and LDLTS spectra of the samples, four predominant electron traps were observed. On the basis of the obtained electrical parameters and previously published results, one of the traps was associated with N-related complex defects, while the other traps with common GaAs-like native defects and impurities, called EL6, EL3 and EL2.

Characterization of deep level defects and thermally stimulated depolarization phenomena in La-doped TlInS2 layered semiconductor

Lanthanum-doped high quality TlInS2 (TlInS2:La) ferroelectric-semiconductor was characterized by photo-induced current transient spectroscopy (PICTS). Different impurity centers are resolved and identified. Analyses of the experimental data were performed in order to determine the characteristic parameters of the extrinsic and intrinsic defects. The energies and capturing cross section of deep traps were obtained by using the heating rate method. The observed changes in the Thermally Stimulated Depolarization Currents (TSDC) near the phase transition points in TlInS2:La ferroelectric-semiconductor are interpreted as a result of self-polarization of the crystal due to the internal electric field caused by charged defects. The TSDC spectra show the depolarization peaks, which are attributed to defects of dipolar origin. These peaks provide important information on the defect structure and localized energy states in TlInS2:La. Thermal treatments of TlInS2:La under an external electric field, which was applied at different temperatures, allowed us to identify a peak in TSDC which was originated from La-dopant. It was established that deep energy level trap BTE43, which are active at low temperature (T ≤ 156 K) and have activation energy 0.29 eV and the capture cross section 2.2 × 10−14 cm2, corresponds to the La dopant. According to the PICTS results, the deep level trap center B5 is activated in the temperature region of incommensurate (IC) phases of TlInS2:La, having the giant static dielectric constant due to the structural disorders. From the PICTS simulation results for B5, native deep level trap having an activation energy of 0.3 eV and the capture cross section of 1.8 × 10−16 cm2 were established. A substantial amount of residual space charges is trapped by the deep level localized energy states of B5 in IC-phase. While the external electric field is applied, permanent dipoles, which are originated from the charged B5 deep level defects, are aligned in the direction of the applied electric field and the equilibrium polarization can be reached in a relatively short time. When the polarization field is maintained, while cooling the temperature of sample to a sufficiently low degrees, the relaxation times of the aligned dipoles drastically increases. Practically, frozen internal electric field or electrets states remain inside the TlInS2:La when the applied bias field is switched off. The influence of deep level defects on TSDC spectra of TlInS2:La has been revealed for the first time.

Characterization of deep level defects in Tl6I4S single crystals by photo-induced current transient spectroscopy

Defect levels in semi-insulating Tl6I4S single crystals grown by the horizontal Bridgman technique have been characterized using photo-induced current transient spectroscopy (PICTS). These measurements revealed six electron traps located at (0.059 ± 0.007), (0.13 ± 0.012), (0.31 ± 0.074), (0.39 ± 0.019), (0.62 ± 0.110), and (0.597 ± 0.105). These defect levels are attributed to vacancies (VI, VS) and antisite defects (IS, TlS, TlI) upon comparison to calculations of native defect energy levels using density functional theory and defects recently reported from photoluminescence and photoconductivity measurements.

Characterization of deep level defects in sublimation grown p-type 6H-SiC epilayers by deep level transient spectroscopy

In this study deep level transient spectroscopy has been performed on boron–nitrogen co-doped 6H-SiC epilayers exhibiting p-type conductivity with free carrier concentration (NA–ND)∼3×1017cm−3. We observed a hole H1 majority carrier and an electron E1 minority carrier traps in the device having activation energies Ev+0.24eV, Ec −0.41eV, respectively. The capture cross-section and trap concentration of H1 and E1 levels were found to be (5×10−19cm2, 2×1015cm−3) and (1.6×10−16cm2, 3×1015cm−3), respectively. Owing to the background involvement of aluminum in growth reactor and comparison of the obtained data with the literature, the H1 defect was identified as aluminum acceptor. A reasonable justification has been given to correlate the E1 defect to a nitrogen donor.

Detailed characterization of deep level defects in InGaN Schottky diodes by optical and thermal deep level spectroscopies

Schottky diode properties of semitransparent Ag(4 nm)/Au(4 nm) metal stack on In0.2Ga0.8N were investigated and defect characterization was performed using capacitance deep level transient (DLTS) and optical spectroscopy (DLOS). DLTS measurements made on the In0.2Ga0.8N Schottky diodes, which displayed a barrier height of 0.66 eV, revealed the presence of two deep levels located at Ec-0.39 eV and Ec-0.89 eV with nearly identical concentrations of ∼1.2 × 1015 cm−3. Three deeper defect levels were observed by DLOS at Ec-1.45 eV, Ec-1.76 eV, and Ec-2.50 eV with concentrations of 1.3 × 1015cm−3, 3.2 × 1015cm−3, and 6.1 × 1016 cm−3, respectively. The latter, with its high trap concentration and energy position lying 0.4 eV above the valance band, suggests a possible role in compensation of carrier concentration, whereas the mid-gap positions of the other two levels imply that they will be important recombination-generation centers

Optical Characterization of Deep Level Defects in SiC

Deep levels in 4H- and 6H-SiC are characterized by FTIR spectroscopy. Vanadium, chromium and the silicon vacancy related center are listed together with the unidentified defects with emission and absorption in the near IR region. We suggest the UD-1, UD-3 and I-1 to be impurity related while the UD-2 and UD-4 to be intrinsic defects based on annealing behavior and the possibility to create the defect with irradiation. We have also tentatively assigned a new defect center around 1.0 eV to the carbon vacancy-antisite pair instead of the earlier assignment to the UD- 2 defect in 4H-SiC. We have shown that to get more information about the SiC samples a combination of absorption and luminescence techniques are very useful. Further, the use of below bandgap selective excitation is necessary to obtain more information about the defects present in the sample. FTIR absorption and luminescence measurements are useful tools to characterize deep levels important for both semi-insulating material as well as low doped conducting material where the free carrier lifetime is limited by deep levels.

Characterization of deep level defects in Si irradiated with MeV Ar+ ions using constant capacitance time analyzed transient spectroscopy

An isothermal spectroscopic technique called time analyzed transient spectroscopy (TATS) in the constant capacitance (CC) mode has been used to characterize electrically active defects in the MeV Ar+ implanted silicon. The problems associated with high defect density and the presence of damaged region in the as-implanted material are overcome by CC-TATS method. The CC-TATS spectra of the as-implanted sample shows two positive peaks and an attendant negative peak. Two distinct traps have also been identified using thermally stimulated capacitance method modified to operate in constant capacitance mode. Variable pulse width measurements using CC-TATS show exponential capture kinetics in contrast to extremely slow capture observed in conventional deep level transient spectroscopy (DLTS) experiment. The results indicate that trapping behaviour is due to point-like defects associated with extended defects such as dislocation and stacking fault.

Characterization of Deep Level Defects in 4h and 6H SIC Via DLTS, SIMS And MEV E-Beam Irradiation

AbstractElectrically active defects in both 4H and 6H polytypes of SiC have been observed through the use of deep level transient spectroscopy (DLTS). Schottky contacts were grown by vapor phase epitaxy (VPE) with doping concentrations, the epitaxial layer having a doping concentration in the range of 1014 cm−3 to 1017cm−3. Numerous levels have been found in the as-grown n-type 6H-SiC samples and secondary ion mass spectrometry (SIMS) and MeV electron irradiation have been employed to corrrelate the defect levels to impurities or structural defects. In contrast, only a single level is observed in the as-grown 4H-SiC samples.

Characterization of deep level defects in thermally annealed Fe-doped semi-insulating InP by thermally stimulated current spectroscopy

The evaluation of deep defects in unannealed and annealed Fe-doped semi-insulating InP was studied using thermally stimulated current (TSC) and photoluminescence (PL) methods. Four TSC peaks with an ionization energy of 0.16, 0.23, and 0.42 eV, respectively, are observed clearly at an annealing temperature ranging from 400 to 700 °C. A 0.42 eV trap is associated with a deep phosphorous vacancy complex defect. 0.16 and 0.32 eV traps are related to the 917 and 888 nm PL emissions, respectively. These emissions are attributed to the deep-donor-acceptor pair transition and exciton bound to a deep level acceptor, respectively, while the 0.23 eV trap is likely to be buried in a broad TSC peak observed in a starting sample.

Characterization of deep level defects in thermally annealed Fe-doped semi-insulating InP by photoinduced current transient spectroscopy

Photoinduced current transient spectroscopy has been used to show the effect of thermal annealing on deep level defects in semi-insulating Fe doped InP wafers. The annealing experiments have been accomplished in an infrared image furnace during 15 min at temperatures ranging from 663 to 820 °C. We show that this treatment leads to the formation of four deep traps named T1–T4 having the following activation energies: 0.14, 0.21, 0.41, and 0.53 eV, respectively. We show that the thermal anneal at high temperature leads to deterioration of the electrical properties of the material.

Characterization of Deep-Level Defects in Semi-Insulating GaAs and InP by Photoinduced Transient Spectroscopy (PITS)

AbstractDeep states in semi-insulating (SI) materials :GaAs:Cr ,un-doped GaAs and InP:Fe are investigated by Photoinduced Transient Spectroscopy (PITS) .The relationship between the Hall mobility in undoped SI GaAs and occurrence of the EL2-related peak in the PITS spectrum is shown.

Characterization of deep-level defects in In1−xGaxAs/InP

New characterization data are presented for the deep-level defects observed in photoluminescence (PL) spectra of InGaAs near 0.1 eV within the band gap. The literature regarding these defects is summarized and compared to the results of this study. Defects are seen to be present in In-rich, Ga-rich, and lattice-matched In1−xGaxAs/InP epilayers. The PL spectra vary depending on alloy composition and crystal growth conditions. PL spectra at 77 K for 0.46<x<0.50 and input laser powers of 9–18 W/cm2 are given for material grown by organometallic vapor phase epitaxy. Hall mobility and Auger electron specroscopy data are also give for these epilayers. The cause of the defects is unknown, but it is not InP substrate doping or growth impurities. Imperfect arsenic incorporation may be involved, as evidenced by the dependence of PL spectra on growth conditions.

Deep-level defects and diffusion length measurements in low energy proton-irradiated GaAs

A detailed characterization of deep-level defects induced by low energy proton irradiation in n-GaAs LPE layer using AlGaAs-GaAs mesa structure has been carried out for several proton energies (i.e., 50 100 and 290 kev) and fluences (i.e., 1010, 1011, and 1012 p/cm2), using DLTS, SEM-EBIC, I-V and C-V measurement techniques. Important defect and recombination parameters such as density and energy level of electron and hole traps, thermal emission rates and capture cross sections for electrons and holes in each trap level as well as hole diffusion lengths in the n-GaAs LPE layer were deduced from these measurements. Hole diffusion lengths determined by the EBIC, DLTS, and I-V measurements are found in good agreement. It is shown that dark current under forward bias condition was dominated by recombination of electron-hole pairs via deep level defects in the junction space charge region of the diode. Significant carrier removal occurs for proton fluence greater than 1013p/cm2.