Apparent Capture Cross Section Research Articles

Characterization of a Metastable Defect Introduced In Epitaxially Grown Boron Doped Si by 5.4 Mev α-Particles

AbstractDeep level transient spectroscopy (DLTS) was used to examine the metastability of a defect configuration in epitaxially grown boron-doped p-type Si. We report the detection of a new metastable defect Hα2 in p-Si following room temperature alpha particle irradiation. DLTS measurements coupled with bias-on/bias-off cooling cycles were used to study the annealing and introduction kinetics of this metastable defect. After removing Hα2 by zero-bias annealing at room temperature, it was re-introduced by reverse bias annealing in the 240-265 K temperature range under predominantly first order kinetics. The energy level and apparent capture cross section, as determined by DLTS, were E,+ 0.43 eV and 1.4 × 10−15 cm2, respectively.

Characterization of Ti2+/Ti3+ donor level in ZnSe by isothermal capacitance transient spectroscopy

The thermally ionized process of the Ti2+/Ti3+ donor level in Ti-doped ZnSe crystals grown by the vertical gradient freezing method was first analyzed with detailed isothermal capacitance transient spectroscopy. The ionization enthalpy and an apparent electron capture cross section of the trap observed from the Arrhenius plot of the emission time constant were 1.058±0.005 eV and (1.03±0.15)×10−12 cm2, respectively. The temperature dependence of the capture cross section of the ionized Ti3+ state revealed a lattice relaxation energy of 0.29±0.03 eV. The real depth of the donor level was determined to be 0.77 eV below the conduction band.

Minority- and majority-carrier trapping in strain-relaxed Ge0.3Si0.7/Si heterostructure diodes grown by rapid thermal chemical-vapor deposition

Strain-relaxed Ge0.3Si0.7/Si, grown by rapid thermal chemical-vapor deposition, has been investigated with deep-level transient spectroscopy (DLTS) and bias-dependent electron-beam-induced current (EBIC). A single electron trap and several hole traps have been detected in these samples. The apparent electron capture cross section is found to be ∼2×10−13 cm2, which is several orders of magnitude larger than the apparent hole capture cross sections (∼10−17 cm2), and is responsible for the detection of the minority-carrier electron trap even under reverse-bias majority-carrier capture conditions. All observed traps which were investigated as a function of filling pulse time exhibit logarithmic capture kinetics, as expected for extended defects, and the bias-dependent DLTS peak height and EBIC relative defect contrast are consistent with the spatially varying dislocation density. Moreover, the trap concentration, as determined by DLTS, is correlated to the dislocation density, as determined by EBIC measurements. Based on a comparison of Arrhenius plots, the observed logarithmic capture kinetics, the correlation of trap density to dislocation density, and the observed bias dependence, the electron trap appears to be related to dislocation core states, while two of the hole traps appear to be related to either dislocation core states or Cottrell atmospheres.

Investigation of the CaF 2/ p-type Si(100) interface by conductance and deep level transient spectroscopy

The electrical properties of the CaF 2/ p-type-Si(100) interface were investigated using capacitance and conductance methods and also by DLTS. It was found that the capacitance-voltage characteristics are frequency dependent. A trap density of about 10 12 cm −2 per unit area and an apparent capture cross section as large as 10 −9 cm −2 were found in the midgap region. From DLTS measurements, we found a strong energy dependence of the apparent capture cross section. The capture cross section and the density of states decrease for levels close to the valence band. Results are explained in terms of carrier transfer between traps located in the insulating material and those in the semiconductor.

Deep level transient spectroscopy measurement on tin-doped n-indium selenide

Deep level transient spectroscopy measurements in indium selenide samples doped with different amounts of tin are reported. Three tin-related electron traps have been detected with activation energies for emission of 56, 74, and 110 meV. The capture cross-section has also been measured and it is very low and weakly dependent on temperature for the 74 and 110 meV deep levels that are attributed to electron trap states related to ionized acceptor centers. For the 56 meV level the apparent capture cross-section shows an activated temperature dependence with an activation energy of 35 meV, which yields an ionization energy of 21 meV for the related level, which corresponds to the tin-related shallow donor. That behaviour is interpreted through the presence in InSe of stacking-fault-related barriers. When one of these barriers is swept by the depletion zone edge during the emptying or filling pulses, electrons must overcome that barrier in order to be emitted or captured, which results in a reduction of the effective capture and emission rates of shallow donors which thus become observable through capacitance transients.

Physical properties of the deep X electron trap responsible for long time persistent photocapacitance in CdS

We describe the main physical properties of a very deep electron trap which is responsible for the long time persistent photocapacitance of Schottky diodes on undoped CdS single crystals. TSCAP and DLTS have been used to determine the apparent thermal activation energy Ea = 0.925 eV and the apparent electron capture cross section σ∞ = 5.5. 10-15cm2 of these centers. Photocapacitance measurements have been performed at various temperatures to allow the determination of the spectral dependence of the photoionisation cross section. The deduced optical threshold En° of the “bound state to the free conduction band state” transition is 2.5 eV. This transition gives a long tail absorption near the fundamental edge which is unambigously identified by the thermal emptying of the X centres. The large difference between Ea = 0.925 eV and En° = 2.5 eV is explained in the large lattice relaxation model. These values are consistent with the results of experiments which locate the X centres, under quasi-equilibrium conditions, at 0.87 eV below the conduction band. They also agree with the results of direct measurement of the thermal activation energy of the electron capture cross section EB = 0.2 eV. The low temperature quenching of both electron emission and capture is responsible for very large persistent photocapacitance effects which suggest that these X centres are acceptor like and probably correlated with cadmium vacancies.

Transient capacitance spectroscopy in polycrystalline silicon

We have performed deep level transient spectroscopy (DLTS) on 5 Ω cm p-type polycrystalline silicon. Typical DLTS spectra exhibit three peaks centered at 250, 300, and 340 K. The density of states which is estimated from these spectra is found to extend from 0.18 eV of the valence band with a density ∼ 2×1015 eV−1 cm−2. Measurements of capture rates have shown a characteristic trap filling time of ∼10−3 s corresponding to an apparent capture cross section of the order of 10−21 cm2. Studies of the passivation (in a deuterium plasma) of these boundary states have also been made. In that case, the DLTS spectra present only one significant peak at 245 K; the density of states of the unpassivated material is reduced to localized states centered at 0.32 eV from the valence band with a concentration of 5.6×1014 cm−2. The capture cross section of these states is 3.7×10−20 cm2.

Thermally Stimulated Current from Polyethylene in High-Temperature Region

Thermally stimulated current (TSC) is obtained with a small external electric field from low and high density polyethylenes which have been treated by a high-field application. Two peaks, P1 and P2, appear at about 85° and 50°C, respectively. The decay time constant of trapped charges is also obtained from the isothermal decay experiment which is compared with that estimated from the TSC curve. For the peak P1, a consideration on both the activation energies and the relation between the apparent capture cross section and the nature of life-time suggests that the trap is surrounded by a potential barrier. For the peak P2, the traps exist in the amorphous-crystalline interface and the release of the trapped charges is enhanced by the molecular motion.