GaN–InGaN LED efficiency reduction from parasitic electron currents in p-GaN

Abstract

This paper presents observations of a previously unidentified source of performance limitation for GaN–InGaN LED devices. While most studies focus on output saturation known as ‘current droop’ from InGaN layer effects, we show an alike influence from p-type GaN’s inherent background electron concentration. p-GaN material was investigated to confirm that, even though the material had an excess of holes, the background electrons were indeed present and were influencing the charge flow across device electrodes. This current does not cross LED heterojunctions but rather drifts toward its proximal device electrode, causing a source of heating while providing no carriers for light emitting recombination. The effects of this current were explored in an LED configuration, whose output showed weak efficiency at very low biases in addition to that from current droop. While the shortcoming under small currents has previously been attributed to electron tunneling across the junction, we propose that the background electrons inside p-GaN could be another explanation.