Epitaxial layers of α-Ga2O3 with different Sn doping levels were grown by halide vapor phase epitaxy on sapphire. The films had shallow donor concentrations ranging from 1017 to 4.8 × 1019 cm−3. Deep level transient spectroscopy of the lowest doped samples revealed dominant A traps with level Ec − 0.6 eV and B traps near Ec − 1.1 eV. With increasing shallow donor concentration, the density of the A traps increased, and new traps C (Ec − 0.85 eV) and D (Ec − 0.23 eV) emerged. Photocapacitance spectra showed the presence of deep traps with optical ionization energy of ∼2 and 2.7 eV and prominent persistent photocapacitance at low temperature, surviving heating to temperatures above room temperature. The diffusion length of nonequilibrium charge carriers was 0.15 µm, and microcathodoluminescence spectra showed peaks in the range 339–540 nm, but no band-edge emission.

No abstract

Analysis of AlN/AlGaN/GaN metal-insulator-semiconductor structure by using capacitance-frequencytemperature mapping Appl. Phys. Lett. 101, 043501 (2012); 10.1063/1.4737876 Deep traps in AlGaN/GaN heterostructures studied by deep level transient spectroscopy: Effect of carbon concentration in GaN buffer layersA set of AlGaN/AlN/GaN high electron mobility transistor structures with Al composition in the AlGaN barrier changing from 20% Al to 50% Al was grown by metalorganic chemical vapor deposition on sapphire and studied by capacitance-voltage (C-V) measurements, admittance spectroscopy, and deep level transient spectroscopy. C-V and admittance measurements were performed in the dark and after illumination. The results suggest the presence of high concentrations of deep negatively charged traps in the AlGaN barriers, producing shifts of the C-V characteristics to more positive voltages. The density of negatively charged centers can be increased by cooling at high reverse bias. These centers have a high barrier for the capture of electrons. Their thermal activation energy is estimated as 0.85 eV, while the optical ionization energy is $1.7 eV.

No abstract

No abstract