Влияние нейтронного облучения на спектр дефектов с глубокими уровнями в GaAs, изготовленном методом жидкофазной эпитаксии в атмосфере водорода и аргона

The results of experimental studies of capacitance– voltage characteristics, spectra of deep-level transient spectroscopy of graded high-voltage GaAs p+−p0−i−n0 diodes fabricated by liquid-phase epitaxy at a crystallization temperature of 900C from one solution–melt due to autodoping with background impurities, in a hydrogen or argon ambient, before and after irradiation with neutrons. After neutron irradiation, deep-level transient spectroscopy spectra revealed wide zones of defect clusters with acceptor-like negatively charged traps in the n0-layer, which arise as a result of electron emission from states located above the middle of the band gap. It was found that the differences in capacitance–voltage characteristics of the structures grown in hydrogen or argon ambient after irradiation are due to different doses of irradiation of GaAs p+−p0−i−n0 structures and different degrees of compensation of shallow donor impurities by deep traps in the layers.

Deep level transient spectroscopy and photoluminescence studies of hole and electron traps in ZnSnP2 bulk crystals

ZnSnP2, an emerging inorganic material for solar cells, was characterized by deep level transient spectroscopy (DLTS) and photoluminescence (PL). Acceptor- and donor-like traps with shallow energy levels were detected by DLTS analysis. The previous study based on first-principle calculation also suggested such traps were due to antisite defects of Zn and Sn. PL measurements also revealed sub-gap transitions related to these trap levels. Additionally, DLTS found a trap with deep level in ZnSnP2. A short lifetime of minority carrier in previous work might be due to such trap, coming from phosphorus vacancies and/or zinc interstitials suggested by first-principle study.

Space charge capacitance study of GaP/Si multilayer structure grown by plasma deposition

Microcrystalline GaP/Si multilayer structures grown on GaP substrates using combination of PE-ALD for GaP and PECVD for Si layers deposition are studied by three main space charge capacitance techniques: C-V profiling, admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS), which have been used on Schottky barriers formed on the GaP/Si multilayer structures. C-V profiling qualitatively demonstrates an electron accumulation in the Si/GaP wells. However, quantitative determination of the concentration and spatial position of its maximum is limited by the strong frequency dependence of the capacitance caused by electron capture/emission processes in/from the Si/GaP wells. These processes lead to signatures in AS and DLTS with activation energies equal to 0.39±0.05 eV and 0.28±0.05 eV, respectively, that are linked to the energy barrier at the GaP/Si interface. It is shown that the value obtained by AS (0.39±0.05 eV) is related to the response from Si/GaP wells located in the quasi-neutral region of the Schottky barrier, and it corresponds to the conduction band offset at the GaP/Si interface, while DLTS rather probes wells located in the space charge region closer to the Schottky interface where the internal electric field yields to a lowering of the effective barrier in the Si/GaP wells. Two additional signatures were detected by DLTS, which are identified as defect levels in GaP. The first one is associated to the SiGa+VP complex, while the second was already detected in single microcrystalline GaP layers grown by PE-ALD.

M-Center in Neutron-Irradiated 4H-SiC

We report on the metastable defects introduced in the n-type 4H-SiC material by epithermal and fast neutron irradiation. The epithermal and fast neutron irradiation defects in 4H-SiC are much less explored compared to electron or proton irradiation-induced defects. In addition to the carbon vacancy (Vc), silicon vacancy (Vsi) and carbon antisite-carbon vacancy (CAV) complex, the neutron irradiation has introduced four deep-level defects, all arising from the metastable defect, the M-center. The metastable deep-level defects were investigated by deep level transient spectroscopy (DLTS), high-resolution Laplace DLTS (L-DLTS) and isothermal DLTS. The existence of the fourth deep-level defect, M4, recently observed in ion-implanted 4H-SiC, has been additionally confirmed in neutron-irradiated samples. The isothermal DLTS technique has been proven as a useful tool for studying the metastable defects.

Investigation of defects in structures based on BP/Si heterojunction

In this work the properties of the BP/Si heterojunction interface were investigated by capacitance methods, the deep levels transient spectroscopy method and admittance spectroscopy. Admittance spectroscopy did not detect any defects, but the deep level transient spectroscopy showed response with activation energy of 0.33 eV and capture cross-section σn=(1-10)·10-19 cm2 and defect concentration (NT) is in the order of 1013 cm-3. This defect level is a trap for electron with position of 0.33 eV below the conduction band in region near the BP/Si interface.

Technology computer aided design based deep level transient spectra: Simulation of high-purity germanium crystals

Very often Deep Level Transient Spectroscopy (DLTS) specimens deviate from ideal textbook examples making the interpretation of spectra a huge challenge. This challenge introduces inaccurate estimates of the emission signatures and the lack of appropriate estimates for the concentrations of the observed trap levels. In this work it is shown with the example of high-purity germanium that Technology computer aided design including symbolic differentiation provides the necessary numerical stability over a wide temperature range to model DLTS spectra. Moreover this high-purity germanium is a quasi intrinsic semiconductor for which it is well-known that the original small signal theory can introduce strong errors. It is furthermore shown that the parasitic impact of fractional filling and high resistivity material can be modelled and that these modelled spectra can in the future assist the interpretation of experimental results.