Impacts of Si-doping and resultant cation vacancy formation on the luminescence dynamics for the near-band-edge emission of Al0.6Ga0.4N films grown on AlN templates by metalorganic vapor phase epitaxy

Abstract

Luminescence dynamics for the near-band-edge (NBE) emission peak at around 250 nm of c-plane Si-doped Al0.6Ga0.4N films grown on AlN templates by low-pressure metalorganic vapor phase epitaxy were studied using deep ultraviolet time-resolved photoluminescence and time-resolved cathodoluminescence spectroscopies. For the films with the Si-doping concentration, [Si], lower than 1.9 × 1017 cm–3, the doping lessened the concentration of cation vacancies, [VIII], through the surfactant effect or the aid of the reactant doping in a form of H3SiNH2. However, the room-temperature nonradiative lifetime, and, consequently, the equivalent value of internal quantum efficiency in the weak excitation regime steeply decreased when [Si] exceeded 1018 cm−3. Simultaneously, the intensity ratio of the deep-state emission band to the NBE emission abruptly increased. Because the increase in [Si] essentially gives rise to the increase in [VIII] (for [Si]>1.9×1017 cm−3) and the overcompensation of Si is eventually observed for the film with [Si] = 4.0 × 1018 cm−3, the formation of acceptor-type native-defect complexes containing Si such as VIII-SiIII is suggested.

The role of the carbon-silicon complex in eliminating deep ultraviolet absorption in AlN

“…35 For instance, positron annihilation spectroscopy experiments have shown evidence that complexes between vacancies and donor impurities exist and are associated with specific near-UV emissions in AlN and AlGaN. [35][36][37] Previous theoretical studies of point defect complexes in the nitrides have investigated the stability of vacancy complexes, 28 impurity complexes involving Mg, 24,25,38,39 and nearest neighbor pairs (e.g., C N -C Al , Si N -Si Al ). 40 One DFT study using standard functionals examined the binding energy of neutral nC N -Si Al (n ¼ 1-4) complexes in AlN as compared to the neutral C N and Si Al isolated point defects.…”

High-quality n-type aluminum gallium nitride thin films grown by interrupted deposition and in-situ thermal annealing

“…Chichibu et al [18] have reported that the intensity of NBE emission (I NBE ) of Al 0.6 Ga 0.4 N:Si films on AlN template decreased clearly with the increase of the doping concentration of Si, when the doping concentration of Si was elevated to above 1 Â 10 18 cm À 3 . The intensity ratio of the NBE emission to the deep level emission (I NBE /I deep ) even abruptly decreased to nearly 0.01 when the doping concentration of Si reached 4.0 Â 10 18 cm À 3 .…”

“…However, when the Si doping was divided into multi-periods and each was followed by an in-situ thermal annealing, the electron concentration reached to 1.1 Â 10 19 cm À 3 and the mobility was promoted to 4.8 cm 2 /V s for sample B. It is known that Al vacancies (V Al ) are the major vacancy defects in Al x Ga 1 À x N alloys [18], the substitutional impurities (Si Al ) can be formed by the thermal annealing. First, the in-situ thermal annealing at higher temperatures cannot only reduced the defects including dislocations, but provided the energy to ionize the donors and drove them into the substitutional sites.…”

“…Unfortunately, these samples were thicker than 1 μm to incorporate more Si dopants and had poor crystalline qualities and poor optical properties. Chichibu et al [18] investigated the near-band-edge (NBE) emission spectra of Al 0.6 Ga 0.4 N alloys at various doping concentrations of Si (7.5 Â 10 16 -4.0 Â 10 18 cm À 3 ). Their samples showed a very low TD density on AlN templates prepared by MOCVD.…”

Investigation of Boron Containing AlN and AlGaN Layers Grown by MOVPE

“…We attribute the broad band ranging from 3 eV to 4 eV to silicon, oxygen and carbon related defects and their complexes. Their intensities are not strongly influenced by the layer thickness, despite the roughening of the surface which could have indicated a deterioration of the crystal quality and increase in structural defects.…”