Absorption coefficient, energy gap, exciton binding energy, and recombination lifetime of GaN obtained from transmission measurements

Abstract

The absorption coefficient for a 0.4-μm-thick GaN layer grown on a polished sapphire substrate was determined from transmission measurements at room temperature. A strong, well defined exciton peak for the A and B excitons was obtained. The A, B, and C excitonic features are clearly defined at 77 K. At room temperature, an energy gap Eg=3.452±0.001 eV and an exciton binding energy ExA,B=20.4±0.5 meV for the A and B excitons and ExC=23.5±0.5 meV for the C exciton were determined by analysis of the absorption coefficient. From this measured absorption coefficient, together with the detailed balance approach of van Roosbroek and Shockley, the radiative constant B=1.1×10−8 cm3/s was obtained.

Ultrafast carrier relaxation in GaN,In0.05Ga0.95N,and anÖzgür1, Everitt2 2003Phys. Rev. B

“…The rate of this decay is observed to be slower than 300 ps, which is consistent with the recombination lifetimes obtained for GaN. 21,27 B. Differential transmission of an In0.05Ga0.…”

“…3b), the generation of carriers may seem more surprising, especially because it cannot be explained as an assist from room temperature thermal energy k B T (26 meV) or from the pulse bandwidth (25 meV). It is well known that the excitonic resonances are visible even at room temperature for GaN 21 , and AC Stark effect has been observed for GaN for detunings as large as 159 meV below the exci- tonic resonance. 28 The bleaching which exists during the intense pump pulse and lasts less than 500 fs is an indication of the AC Stark effect.…”

Determination of band offsets at GaN/single-layer MoS2 heterojunction

“…28 Hence, these observed optical bandgap values differ from reported electronic bandgap values of E g SL-MoS 2 ¼ 2.15 eV and E g GaN ¼ 3.45 eV by their respective exciton binding energy (E b ) values of %0.220 eV and %0.023 eV in the literature. 19,29,30 High-resolution XPS measurements are direct, most reliable, and extensively employed to determine the valence band offset (VBO) of a heterojunction interface. In order to evaluate VBO at GaN/SL-MoS 2 heterointerface, the energy difference between the Ga and Mo core levels from the GaN/ SL-MoS 2 heterojunction sample and the energy of core levels relative to the respective valence band maximum of the GaN epilayer and SL-MoS 2 samples need to be acquired.…”

III-nitride core–shell nanowire arrayed solar cells

“…These properties include the ability to tune the bandgap of InGaN across nearly the entire solar spectrum (0.7eV-3.4eV) [2], high absorption coefficient (~10 5 cm -1 ) [3], and high radiation resistance [4]. In theory these properties, could translate into solar cells with high efficiency, in thin layers, and with long lifetimes.…”