Photoexcited carrier dynamics in AlInN/GaN heterostructures

Abstract

Photoexcited carrier dynamics and localization potentials in Al0.86In0.14N/GaN heterostructures have been examined by time-resolved and scanning near-field photoluminescence (PL) spectroscopy. The large GaN and AlInN PL intensity difference, and the short AlInN PL decay and GaN PL rise times indicate efficient photoexcited hole transfer from AlInN to GaN via sub-band-gap states. These states are attributed to extended defects and In clusters. Near-field PL scans show that diameter of the localization sites and the distance between them are below 100 nm. Spatial variations of the GaN PL wavelength have been assigned to the electric field inhomogeneities at the heterostructure interface.

Carrier dynamics and localization in AlInN/GaN heterostructures

“…Thus, the photoexcited carrier transport can only take place via the subband edge states. The short AlInN PL decay time component is similar to the GaN PL rise time, which, at 4 K, is 8 ps [3]. This correspondence, as well as the relatively long GaN PL rise indicates that PL in the GaN layer is partially generated by carriers arriving from AlInN.…”

“…The PL decay can be described by a doubleexponential. The short decay component decreases from 17 ps at 4 K to 11 ps at 280 K. The long component changes from 130 ps to 185 ps in the same temperature range [3]. The short component dominates the transients with the short to long component weight ratio between 20 and 50.…”

“…The map of the GaN peak intensity (Fig. 4(b)) shows much larger variations, that can be attributed to the nonuniform distribution of the nonradiative recombination centres [3]. The GaN PL intensity map may be compared to that of AlInN (Fig.…”

“…In addition, basic material parameters, such as the band gap and the bowing parameter are not well established, and band potential fluctuations and properties of carrier localization are not well understood. For instance, optical studies have revealed a large, up to 1 eV, Stokes shift between absorption and emission [2,3], which is not yet unambiguously clarified. Several reasons might be responsible for that shift.…”

Room temperature photoluminescence from InxAl(1−x)N films deposited by plasma-assisted molecular beam epitaxy

“…26 Because TEM and AFM analysis of our PAMBE In 0.114 Al 0.886 N and In 0.166 Al 0.834 N samples indicate a very low density of V-defects, we infer that carrier transport is mediated by the nanocolumnar microstructure with numerous edge-type threading dislocations. Consequently, some carriers photo-generated in the InAlN film are transported to the GaN templates to generate strong GaN PL, while others become localized in the In-rich boundaries of the InAlN microstructure to generate InAlN PL with large Stokes shifts.…”