Transient photoreflectance of AlInN/GaN heterostructures

Abstract

Time-resolved photoreflectance (PR) in AlInN/GaN heterostructures was applied to study carrier dynamics at energies extending from the uniform AlInN alloy band gap to the band gap of GaN. PR at the AlInN band gap has been found to have subpicosecond decay. Such ultrafast carrier relaxation from the extended to the sub-band edge states implies that the localization sites are small and dense, most probably originating from the In-rich clusters. At energies below the AlInN band gap, a complicated energy dependence of the PR signal is attributed to the properties of the localized states and to the modulation of the interface electric field by photoexcitation.<p>QC 20130109</p

Semiconductor interfacial carrier dynamics via photoinduced electric fields

“…The normalized change in reflectance (DR/R) at different probe photon energies (ħw) was recorded as a function of pump-probe delay. Reflectance modulations could arise from band filling by photogenerated free-carriers (15) and/or transient field changes arising from electro-optic effects (16,17). Pseudocolor images of DR/R as a function of probe photon energy and pump-probe delay are displayed for the three samples in Fig.…”

Development of Quaternary InAlGaN Barrier Layer for High Electron Mobility Transistor Structures

“…The results of the PL measurements (see Figure 6 ) demonstrate a 0.40 eV red-shift from the expected bandgap energy of the quaternary barrier (see Figure 4 a). Such a red-shift of the PL peak was sufficiently small in comparison to the Stokes shifts reported for similar heterostructures with InAlN barrier exhibiting values in the range of 0.4–1 eV [ 36 , 37 , 38 , 39 , 40 ]. Various explanations of the Stokes shift were proposed such as the introduction of sub-band edge states near the band edge minima which induce strain and related alloy composition fluctuations [ 41 ], local variations of the number of Al and In atoms surrounding nitrogen atom [ 42 ] or radiative recombination between the electrons in the triangular quantum well (2DEG) and photoexcited holes efficiently transferred from InAlN to GaN via sub-band-gap states [ 37 ].…”

Properties of sub-band edge states in AlInN studied by time-resolved photoluminescence of a AlInN/GaN heterostructure

“…In this work, as in previous PL measurements [4][5][6][7][8][9], no PL signal was detected at the energy of the extended state band gap. Time-resolved reflectance measurements showed that this occurs due to ultrafast carrier capture by sub-band edge states [20]. With a trapping time of ∼1 ps, this process is much faster than radiative recombination; thus, most of the carriers leave the band edge states before the recombination.…”