Contribution of the carbon-originated hole trap to slow decays of photoluminescence and photoconductivity in homoepitaxial n-type GaN layers

Abstract

N-type GaN epitaxial layers grown via metal organic vapor-phase epitaxy typically exhibit a yellow luminescence (YL) band owing to carbon-related deep levels in the photoluminescence spectra. The decay of YL after pulse excitation involves a long time constant (∼0.2 ms at room temperature), whereas microwave photoconductivity decay (μ-PCD) curves show the corresponding component of the time constant. To clarify the origin of the long decay time, the temperature-dependent time constants of YL decay and μ-PCD curves are analyzed using a numerical model based on rate equations for trapping and emission through a deep level. The characteristics of the decays are well reproduced by a recombination model using a hole trap H1 at an energy of EV + 0.88 eV because of the acceptor-like state of carbon on a nitrogen site (CN) whose electron capture cross section (σn) is estimated to be 3 × 10−21 cm2. The slow decay in μ-PCD signals indicates that the electrons before being captured to H1 traps are free electrons in the conduction band. These findings indicate that the slow recombination process through CN results in tail currents in the turn-off switching periods of devices.

Spatially and Time-Resolved Carrier Dynamics in Core–Shell InGaN/GaN Multiple-Quantum Wells on GaN Wire

“…Its origin is still under debate: Ga vacancies and/or carbon-related centers are possible candidates. 33 While the YB map reveals a homogeneous distribution in the wire GaN core (which has the largest excited volume), the emission attributed to the MQWs supports previous carrier localization phenomena connected to the hexagonal geometry. 34 The InGaN/GaN MQWs trap carriers and radiate light mainly from the vertices of the hexagon.…”

“…With a 600 meV line width, the YB band is associated with the optical transition between the conduction band (or shallow donor) and deep acceptor with an activation energy of 0.8–0.9 eV. Its origin is still under debate: Ga vacancies and/or carbon-related centers are possible candidates . While the YB map reveals a homogeneous distribution in the wire GaN core (which has the largest excited volume), the emission attributed to the MQWs supports previous carrier localization phenomena connected to the hexagonal geometry .…”

On the Origin of the Yellow Luminescence Band in GaN

“…The strongest arguments in favor of the C N origin of the YL band were presented in experimental works. [64][65][66][67] More details are given in Section 3.8.…”

Unravelling material properties of halide perovskites by combined microwave photoconductivity and time-resolved photoluminescence spectroscopy

“…Furthermore, in contrast to trPL, microwave photoconductivity measurements are highly sensitive to long-lived trap states and thus yield information about the duration that charge carriers stay trapped. 13 This is expected to influence both recombination and transport properties. 10…”