Investigation of Electrical and Optical Characteristics of Micro-Sized Light-Emitting Diodes

Abstract

We investigated the electrical and optical characteristics of InGaN-based green micro light-emitting diodes (LEDs) with different-sized active emission areas, ranging from 90 × 90 μm2 to 37×37 μm2. Our results showed that the reverse and forward leakage currents of micro LEDs substantially increased as their active emission area was reduced. This experimental observation appears to be associated with the Shockley-Read-Hall (SRH)-like non-radiative recombination processes at the sidewall defects, more prominently found in smaller micro LEDs with larger surface-to-volume ratios. The sidewall leakage current deteriorated the injection efficiency of the carriers into quantum wells (QWs) of smaller InGaN micro LEDs, also affecting the size-dependent external quantum efficiency (EQE) behavior. Furthermore, emission microscopy analysis confirmed that the reverse leakage current is originated mostly from the sidewall of the 37 × 37 μm2 micro LEDs. From our results, low-power consuming and further down-scaled micro LED-based mobile displays are available if the sidewall defects of micro LEDs should be more aggressively suppressed.