A direct epitaxial approach to achieving ultrasmall and ultrabright InGaN micro light-emitting diodes (μLEDs)

A direct epitaxial approach to achieving ultrasmall and ultrabright InGaN micro light-emitting diodes (μLEDs) has been developed, leading to the demonstration of ultrasmall, ultraefficient, and ultracompact green μLEDs with a dimension of 3.6 μm and an interpitch of 2 μm. The approach does not involve any dry-etching processes which are exclusively used by any current μLED fabrication approaches. As a result, our approach has entirely eliminated any damage induced during the dry-etching processes. Our green μLED array chips exhibit a record external quantum efficiency (EQE) of 6% at ∼515 nm in the green spectral region, although our measurements have been performed on bare chips which do not have any coating, passivation, epoxy, or reflector, which are generally used for standard LED packaging in order to enhance extraction efficiency. A high luminance of >107 cd/m2 has been obtained on the μLED array bare chips. Temperature-dependent measurements show that our μLED array structure exhibits an internal quantum efficiency (IQE) of 28%. It is worth highlighting that our epitaxial approach is fully compatible with any existing microdisplay fabrication techniques.