Optical properties of conductive and semi-insulating HVPE-GaN crystals

Abstract

Effective doping plays an important part in the marketization of gallium nitride (GaN) devices. Si and Fe are the most widely used doping elements when employing hydride vapor phase epitaxy, which change the electrical properties of GaN and form n-type and semi-insulating GaN after entering the GaN lattice, however, the light absorption caused by dopant atoms has a heavy impact on the performance of GaN optoelectronic devices, whereas the optical properties of Si- and Fe-doped GaN have been neglected. We investigated the macroscopic color differences of different doped elements to explore the reasons for changes in optical properties due to elemental doping. Si-doped GaN was more transparent because it did not produce additional absorption peaks in the visible range and the energy level density of the valence band increased. Fe-doped GaN appeared green because of Fe-3d at the bottom of the conduction band, which led to light absorption. Exciton recombination in the impurity energy levels led to the formation of intense green emission bands and absorption centers. Exploration of optical properties could provide a theoretical basis for the subsequent production of GaN optoelectronic devices.