Radiative carrier lifetime, momentum matrix element, and hole effective mass in GaN

Abstract

By using picosecond time-resolved photoluminescence we have measured the lifetime of excess charge carriers in GaN epitaxial layers grown on sapphire at temperatures up to 300 K. The decay time turns out to be dominated by trapping processes at low excitation levels. The radiative lifetime derived from our data is dominated by free excitons at temperatures below 150 K, but also clearly shows the gradual thermal dissociation of excitons at higher temperatures. From our data, we are able to determine the free exciton binding energy and the free carrier radiative recombination coefficient. By combining these data with optical absorption data, we find the interband momentum matrix element and an estimate for the hole effective mass, which is much larger than previously thought.

Temperature-Dependence of Exciton Radiative Recombination in (Al,Ga)N/GaN Quantum Wells Grown on a-Plane GaN Substrates

“…22, the E a obtained from temperature-dependent PL experiments cannot be directly compared to the electron and hole confinement energies. When aiming at describing the thermal escape of carriers from a QW, one needs to account for (i) the ionization of excitonic complexes into electron-hole pairs, 10,23) (ii) the difference in density of states between the (Al,Ga)N barriers and the GaN QW (three and two dimensional, respectively), 10) (iii) B and C excitons, as well as the excited states of the three exciton branches 22) and (iv) the disorder in both the QW plane and the (Al,Ga)N barriers. 10,23) As expected, we manage to fit the temperature dependence of PL for the different excitation spots keeping a constant E a , which we find equal to 43 meV (Fig.…”

Dopant-induced band filling and bandgap renormalization in CdO : In films

“…A large spread was found for GaN and InN. For GaN, E P ranges from about 7.7 eV [22] to a maximum value of 18.6 eV [16], and InN shows E P about 9.5 eV~18 eV [14,23]. Taking E P =6.5 eV into equation (1), the conduction band dispersion energy of CdO can be obtained.…”

Effects of the narrow band gap on the properties of InN

“…It can be seen that although the effective mass data were reported by different groups on InN films grown by different methods, the calculation using E P = 10 eV shows reasonably good agr eement with all the measured data points. For comparison, we note that E P values for wurtzite GaN as low as 7.7 eV [18] and as high as 14 eV [19] have been reported in the literature. The extrapolation of the curve leads to an effective mass of 0.07m 0 at the bottom of the conduction band.…”