Vacancy compensation and related donor-acceptor pair recombination in bulk AlN

Abstract

A prominent 2.8 eV emission peak is identified in bulk AlN substrates grown by physical vapor transport. This peak is shown to be related to the carbon concentration in the samples. Density functional theory calculations predict that this emission is caused by a donor-acceptor pair (DAP) recombination between substitutional carbon on the nitrogen site and a nitrogen vacancy. Photoluminescence and photoluminescence-excitation spectroscopy are used to confirm the model and indicate the DAP character of the emission. The interaction between defects provides a pathway to creating ultraviolet-transparent AlN substrates for optoelectronics applications.

Deep traps in GaN-based structures as affecting the performance of GaN devices

“…Straight Hall effect/conductivity measurements are relatively easy for Al mole fractions x < 0.2. For higher compositions p-type conductivity has only been reported for carefully optimized growth conditions minimizing the impact of compensating centers among which the prominent role of nitrogen vacancies has been noted (we'll return to this point later) [124][125][126][127][128].…”

“…20. More realistically, in AlN where it is difficult to move the Fermi level close to the valence band, one would deal with the V N + single donors with the charge transition level near 1 eV from the conduction band edge (see [127] and Fig. 22).…”

“…Additional PL band at 2.8 eV was ascribed to the donor-acceptor pairs (DAP) transition between the C N À acceptors near E v +2 eV and singly charged V N + deep donors with the charge transfer level near E c À1 eV according to calculations in Ref. [127]. The authors argue that, at high growth temperatures and high C density, the concentrations of V N + can be close to the concentration of C N À , particularly under the Al-rich growth conditions.…”

Defect mechanisms of coloration in Fe-doped SrTiO3 from first principles

“…), while further analysis was performed by solving relevant charge balance equations as done previously. 48,49 Configurational entropy is accounted for in the defect concentration expression prefactor through the number of identical configurations. Vibrational, electronic, and magnetic entropy are neglected due to their small expected contributions relative to other terms in the formation energy expression and the significant expense required to capture these energies for each charged defect.…”

“…If growth was simulated, care should be taken to ensure that impurity chemical potential limits were not exceeded. 49,51,52 For annealing, it was assumed the temperature would not be high enough to change the dopant content of the crystal. During the anneal, defect concentrations were calculated as a function of chemical potential.…”