Laplace DLTS studies of the 0.25 eV electron trap properties in n-GaN

Abstract

The thermal emission rate of electrons from a 0.25 eV trap, widely observed in epitaxial GaN by conventional deep-level transient spectroscopy (DLTS), is investigated by the Laplace DLTS (LDLTS) technique. It is demonstrated that the capacitance relaxation waveforms, from which the properties of this trap have been determined until now by the correlation procedure, contain two exponential components induced by the thermal emission of electrons from two traps with the activation energies of 173 meV and 232 meV. In lightly silicon-doped and carbon-doped epitaxial GaN grown on sapphire substrates, the concentrations of these traps were found to be (5.5–7.2) × 10¹³ and (1.5–3.2) × 10¹³ cm⁻³, respectively. Based on formerly reported experimental results and recently published results of theoretical calculations performed with the implementation of the density functional theory with hybrid functionals, the point defects being a potential source of these traps is proposed. It is shown, that a high resolution of LDLTS gives a new insight into the properties of energy levels related to point defects in epitaxial GaN.