Articles you may be interested inInterface trap characterization of atomic layer deposition Al2O3/GaN metal-insulator-semiconductor capacitors using optically and thermally based deep level spectroscopies

BSTRACT HAR 1 !3 Kk3!l Deep level transient spectroscopy (DLTS) measurements were utilized to investi ate deep level bsTl defects in metal-organic chemical deposition (MOCVD)-grown unintentionally doped p-tie InGaAsN films lattice matched to GaAs. The as-grown material displayed a high concentration of deep levels distributed within the bandgap, with a dominant hole trap at &+O. 10 eV. Postgrowth annealing simplified the deep level spectra, enabling the identification of three distinct hole traps at 0.10 eV, 0.23 eV, and 0.48 eV above the valence band edge, with concentrations of 3.5x1014 cm-3, 3.8x10*4 cm-3, and 8.2x1014 cm-3, respectively. A direct comparison between the as-grown and annealed spectra revealed the presence of an additional midgap hole trap, with a concentration of 4x 1014cm-3 in the as-grown material. The concentration of this trap is sharply reduced by annealing, which correlates with improved material quality and minority carrier properties after anealing. Of the four hole traps detected, only the 0.48 eV level is not influenced by annealing, suggesting this level maybe important for processed InGaAsN devices in the future.

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The influence of initial growth conditions and lattice matching on the deep level spectrum of n-ZnSe grown on GaAs by molecular-beam epitaxy is investigated by means of deep level optical spectroscopy. A detailed study of both the steady-state and transient photocapacitance allows us to measure optical threshold energies, concentrations, and emission rates of electronically active defects in the ZnSe layer. Several deep levels are found in the ZnSe layer at Ec−Et=1.15, 1.46, 1.90, and 2.25 eV with concentrations in the 1012–1014 cm−3 range. When a 2-nm-thick composition controlled interface layer is grown at different beam pressure ratios prior to the ZnSe growth, a distinct decrease in the 1.46 eV level concentration with increasing Se content is found. Deposition of a lattice-matched InxGa1−xAs buffer layer prior to the ZnSe growth reduces the concentration of both the 1.15 and 1.46 eV levels by over an order of magnitude, indicating the role of lattice matching in the ZnSe overlayer. We also perform depth profiling of the defect distributions within the ZnSe overlayer to see the effect of the ZnSe thickness on the concentration of these levels as well as their possible association to the ZnSe/GaAs interface. We find that only the 2.25 eV level concentration shows a dependence on depth, increasing as the II–VI/III–V interface is approached.

We present the results of studies on the defect properties and the effect of light soaking for various hot wire deposited (HW) films. We employ junction capacitance measurements together with the transient photocapacitance spectroscopy to measure the deep defect densities in as-grown state (state A) and in light soaked state (state B). Good agreement is found between the defect densities measured from both measurements. The HW film with a hydrogen content of 10 – 12 at.% shows physical characteristics and defect densities similar to conventional PECVD films. The HW films with hydrogen content, CH, in the range 2 – 9 at.% show a smaller defect density in state B than the defect density of the film with higher CH. However, the film with a hydrogen level of less than 1 at.% exhibits markedly inferior physical properties.