High-temperature degradation of GaN LEDs related to passivation

This paper describes the thermally activated failure mechanisms of GaN light-emitting diode (LED)-test structures related with the presence of a hydrogen-rich SiN passivation layer. It is shown that the properties of the passivation layer can remarkably affect devices’ stability during high-temperature stress: Degradation mechanisms identified consist of radiative efficiency loss, emission crowding, and forward-current decrease. The radiative efficiency degradation was found to be thermally activated, with activation energy equal to 1.3 eV. This failure mechanism of LEDs is attributed to the thermally activated indiffusion of hydrogen from the passivation layer to p-type region of the diodes, with subsequent p-doping compensation and/or worsening of the transport properties of the p-side ohmic contact and p-type semiconductor.