Electrical Properties, Deep Levels and Luminescence Related to Fe in Bulk Semi-Insulating β-Ga₂O₃ Doped with Fe

Abstract

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.

Hydrogen plasma treatment of β -Ga2O3: Changes in electrical properties and deep trap spectra

“…17,18 If C-V measurements are done at frequencies/temperatures where the step in capacitance is observed, one can calculate the concentration of electrons on the deep levels producing the step. [26][27][28] Such sets of steps in capacitance/peaks in conductance could be observed in the as-hydrogenated sample and the sample annealed at 450 C. Figure 4(a) shows the temperature dependence of capacitance for the as-hydrogenated sample for several low frequencies, while Fig. 4(b) shows respective peaks in conductance [conductance in Fig.…”

“…DLTS was not suitable for measurements on the as-hydrogenated sample and after 450 C annealing because of the high series resistance of these films. Some information on the presence of deep centers could be gleaned from high-temperature/low-frequency admittance spectra measurements and from PICTS measurements, as demonstrated for semi-insulating b-Ga 2 O 3 doped with Fe or Mg. [26][27][28] If the Fermi level in the hydrogenated samples was pinned at deep centers, the static space charge region width would be determined by the concentration of centers that preserved their electrons. [26][27][28] These centers would contribute to capacitance, C, and AC conductance, G, at high temperatures and low frequencies at which the centers can follow the probing electric field in admittance.…”

“…Some information on the presence of deep centers could be gleaned from high-temperature/low-frequency admittance spectra measurements and from PICTS measurements, as demonstrated for semi-insulating b-Ga 2 O 3 doped with Fe or Mg. [26][27][28] If the Fermi level in the hydrogenated samples was pinned at deep centers, the static space charge region width would be determined by the concentration of centers that preserved their electrons. [26][27][28] These centers would contribute to capacitance, C, and AC conductance, G, at high temperatures and low frequencies at which the centers can follow the probing electric field in admittance. [26][27][28] Thus, one would expect capacitance to increase with increasing temperature and decreasing frequency, until it reaches values corresponding to the depletion width determined by the concentration of uncompensated deep centers pinning the Fermi level.…”

“…[26][27][28] These centers would contribute to capacitance, C, and AC conductance, G, at high temperatures and low frequencies at which the centers can follow the probing electric field in admittance. [26][27][28] Thus, one would expect capacitance to increase with increasing temperature and decreasing frequency, until it reaches values corresponding to the depletion width determined by the concentration of uncompensated deep centers pinning the Fermi level. These steps in capacitance should shift to higher temperatures with increasing frequency.…”

Halide Vapor Phase Epitaxy of In2O3 and (In1−xGax)2O3 on Sapphire Substrates and GaN/Al2O3 Templates

“…[ 26 ] The procedure of contact deposition and the measurement setup were described in detail in previous studies. [ 27,28 ]…”