Electrical properties, deep trap spectra, microcathodoluminescence (MCL) and photoluminescence (PL) spectra of bulk semi-insulating Fe doped β-Ga2O3 crystals with ohmic and Schottky contacts were studied. The Fermi level in these crystals is pinned by the Fe acceptor level near Ec-0.8 eV. This level is also dominant in high-temperature admittance spectra and in photo-induced current transient spectroscopy (PICTS) and determines the space charge region width in Schottky diodes. The concentration of the Fe acceptors filled with electrons is (1.3–1.5) × 1017 cm−3 from high-temperature/low-frequency capacitance-voltage C-V profiling and is considerably lower than the Fe concentration introduced by doping, suggesting that a considerable portion of Fe acceptors are not filled with electrons. This is important when considering the possible role of Fe centers in charge trapping in transistors. MCL and PL spectra measurements also revealed the presence of sharp lines near 1.8 eV corresponding to the 4T1→6A1 intracenter transition in Fe3+. Additional deep centers observed in photocurrent spectra had optical ionization thresholds near 1.5 eV and 2.3 eV.
Generation of dislocations during the growth of oxygen precipitates has been used as an alternative way of introduction of dislocation‐related luminescence centers. For this purpose a multistep annealing of Cz Si samples with different initial concentrations of oxygen has been carried out. The analysis of defect density and structure was performed by optical microscopy (OM) and transmission electron microscopy (TEM). The dislocation‐related luminescence (DRL) appeared only after a growth stage, while its intensity strongly depended on the duration of the preliminary nucleation treatment. The duration of growth annealing had a strong influence on the spectral distribution of the DRL intensity. No correlation has been found between a particular defect density, defined by TEM, and the shape of luminescence bands. Therefore, it was concluded that the cause of the gradual DRL transformation is redistribution of oxygen, collected near dislocations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure and low temperature photoluminescence of Si(001) hydrophilic bonded wafers have been studied. Even at minimal misfit angles the observed dislocation related luminescence (DL) did not coincide with the luminescence of isolated dislocations. The dependence of spectral distribution of DL on the dislocation network density has been studied and analyzed on the basic of previously suggested recombination model. A strong dependence of the spectral distribution of DL on the misfit angle has been found. The temperature dependence of different sub bands in DL spectra has been interpreted in the model of successive thermal emptying of upper states. The similar behavior of DL at increasing temperature and increasing density of misfit dislocations has been interpreted in the model of a relative dependence of dislocation related upper states on the distance between dislocations (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The dislocation photoluminescence (DPL) at 4.2 K was studied in germanium (Ge) single crystals of nand p-type with quasi-equilibrium structure of 60° dislocations. The DPL spectra for different samples were decomposed on Gaussian lines (G m -lines) over the range 0.47-0.58 eV characterized by practically the same peak energies E m and the widths under 15 meV. The G-lines with E m ≤ 0.55 eV were ascribed to the radiation of regular segments of 60° dislocations with different stacking fault (SF) widths ∆ between 30 and 90° partials. An increase of the dislocations density up to N D ~ 10 7 cm -2 was found to result in a considerable growth of the intensity of the G-lines with E m <0.513 eV. The factors, which promote the appearance of different ∆ values for quasi-equilibrium 60° dislocation structure, are discussed.1 Introduction DPL in germanium emerging from dissociated 60° dislocations has been shown to be rather sensitive to a SF width ∆ governed by plastic deforming conditions of crystals [1][2][3]. Low temperature and high shear stress (LTHS) deformation of silicon (Si) and Ge single crystals followed by cooling down to room temperature under load results in the appearance of long regular dislocation segments with a SF width ∆ n , increased or decreased relatively to the equilibrium value ∆ 0 and, also, a peculiar discrete DPL spectrum [1][2][3][4][5][6]. For thus prepared Ge samples the DPL spectra consist of a series of narrow (~3 meV width) lines, crowding to the limiting energy E ∝ = 0.55 eV. The line peak energies E n are well described by a single empiric formula [1][2][3]. The authors of [3] proved that the E n energy increases with ∆ n and each narrow line is due to the recombination radiation of long regular segments of 60° dislocations with a definite ∆ n width of SF. In the process photo-excited carriers recombine via the 90° partials and the potential of 30° partials is a disturbance, whose value depends on the distance ∆ n between the two partials [1,3]. The line number n is related to ∆ n by the relation n ≈ (∆ n /a)-6, where a = 0.346 nm is a step of changing ∆ n . The line d8 (n = 8) with E 8 = 0.513 eV corresponds to an equilibrium value of ∆ 0 = 49±0.9 nm [7] and the lines with numbers n < 8 and 8 < n < ∝ occur, respectively, on the left and right sides of the d8 line over the range 0.43 to 0.55 eV. Non-equilibrium ∆ n values and the discrete DPL spectrum disappear after annealing of these samples at temperatures above 150 °C. The dislocation structure called a quasi-equilibrium (or relaxed [6]) one forms under relaxation of internal stresses in the process of cooling down to room temperature of unloaded samples after high temperature and low shear stress deformation as well as after annealing of deformed samples at temperatures above 150 °C. In Ge samples prepared in this way, the DPL spectrum is represented as a wide band over the range 0.43-0.60 eV with non-resolved lines, that could be due to the presence of quasi-equilibrium 60° dislocations with various ∆ values. The experimental result...
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