Time-resolved photoluminescence from defects in n-type GaN

Abstract

Point defects in GaN were studied with time-resolved photoluminescence (PL). The effects of temperature and excitation intensity on defect-related PL have been investigated theoretically and experimentally. A phenomenological model, based on rate equations, explains the dependence of the PL intensity on excitation intensity, as well as the PL lifetime and its temperature dependence. We demonstrate that time-resolved PL measurements can be used to find the concentrations of free electrons and acceptors contributing to PL in n-type semiconductors. V

Point Defects in GaN

“…The quenching is caused by the thermal emission of holes from the shallow acceptor to the valence band. The PL lifetime decreases very similarly to the PL intensity, in agreement with theory (Reshchikov, 2014a).…”

“…(6) in conductive n-type GaN. Then, the concentration of free electrons can be found if the electron-capture coefficient C nA is known (Reshchikov, 2014a). At temperatures above 100 K, the UVL band is quenched with an activation energy of about 180 meV.…”

“…The PL lifetime in n-type GaN reveals important characteristics of the radiative defects, such as the electron-capture cross-section. Indeed, in time-resolved PL experiments, the PL intensity decays exponentially after a laser pulse, with the characteristic time constant τ (Reshchikov, 2014a):…”

Carbon defects as sources of the green and yellow luminescence bands in undoped GaN

“…6. The dependences are very similar to each other and can be fit with the following expressions [14] …”

“…The concentration of free electrons, n, given in Table I for these two samples, is calculated from the PL lifetime of the YL band at room temperature, according to a model presented in Ref. [14], while the direct Hall effect measurements showed an apparent concentration of about three times higher due to the existence of a highly conductive layer near the GaN/sapphire interface [15].…”