Analysis of the red optical emission in cubic GaN grown by molecular-beam epitaxy

Abstract

The red optical emission band in cubic GaN is examined for the first time by cathodoluminescence as well as steady-state and time-resolved photoluminescence. We establish a close analogy between the red emission band in cubic GaN and the yellow emission in wurtzite GaN, and assign it to a donor-acceptor process involving a shallow donor and a deep acceptor with similar ionization energies in both phases. We show a range of properties of the red emission which clearly indicate its donor-acceptor pair origin, namely the blueshift with excitation intensity, the power-law evolution at increasing excitation, and the blueshift with temperature. The line shape of the red band indicates that the deep acceptor is strongly coupled to the lattice. The photoluminescence decay curves show a fast decay at higher energies within the emission band, while at lower energies the decay is much slower, typical of donor-acceptor pair transitions. An analytical expression for the time-dependent emission intensity for donor-acceptor pair transitions in which one of the centers is strongly coupled to the lattice is derived, extending the theory of Thomas et al. ͓Phys. Rev. B 140, A202 ͑1995͔͒. The observed decay curves are found to be well described by the theory using the donor Bohr radius of 1.7 nm, while temperature quenching of the emission gives an activation energy of 15Ϯ5 meV. Evidence of Coulomb attraction between a shallow donor and a deep acceptor is presented. ͓S0163-1829͑99͒07631-6͔ PHYSICAL REVIEW B 15 AUGUST 1999-II VOLUME 60, NUMBER 8 PRB 60 0163-1829/99/60͑8͒/5464͑6͒/$15.00 5464

Characterization of Red Emission in Nominally Undoped Hydride Vapor Phase Epitaxy GaN

“…Between the hexagonal defects both the edge and the red emission show spatial intensity variations (Figure 3a and Figure 3b). Such nonuniformities were earlier reported for edge emission wavelengths only [2] and attributed to threading dislocations. In the present films we have observed these micrometer scale variations for the red emission wavelengths as well.…”

“…In our films, however, the yellow band was absent. The red emission band discussed here should be distinguished from other bands also referred to as "red", these include the red emission in cubic GaN examined by the present authors [2], and the red band in GaN codoped with Mg and Si [3].…”

“…The yellow band with the peak at about 2.2 eV, common in wurtzite GaN, has attracted a significant research effort as it was considered to compete with the technologically desirable edge emission [1]. Its red counterpart in cubic GaN was examined as well [2]. In this work we concentrate on the red emission band present in wurtzite GaN films grown by hydride vapor phase epitaxy (HVPE).…”

Time‐resolved photoluminescence characterization of 2 eV band in AlN

“…In the case when one of the centers is strongly coupled to the lattice, the PL decay at given wavelength is non-exponential as well as the total PL decay [16]. Decrease in PL intensity and faster PL decay at elevated temperatures can be caused by presence of a nonradiative recombination channel which is activated by ionization of donors.…”

Cubic GaN Films on GaAs (001) Substrates without Deep-Level Luminescence Grown by Metalorganic Vapor Phase Epitaxy

“…The orange luminescence peak of 2.1 eV at 300 K, which is slightly higher than that at 6 K (Fig. 2), suggests a D±A-like nature of the orange luminescence [9]. Figures 4a and b) show the surface morphologies of cubic GaN films with the suppressed magnitude and with a significant magnitude of orange luminescence, respectively.…”