SiN interlayer to improve external quantum efficiency and reduce sidewall recombination for blue (micro) light-emitting diodes

We demonstrate that inserting a fractional monolayer of SiN below the first InGaN quantum well (QW) does not change the In content but increases the external quantum efficiency (EQE) of light-emitting diodes (LEDs) and reduces the sidewall recombination, together with a small redshift and slight broadening of the emission. At low currents, we could directly measure the reduced emission from the sidewall of 80 μm diameter circular LEDs by inserting an SiN interlayer. This points to a reduced lateral diffusion of carriers in the QWs via an enhanced composition fluctuation indicated by the broadening of x-ray diffraction satellite peaks in addition to the formation of V-defects. Thus, the SiN interlayer increases the carrier localization in the QWs, which increases the EQE of LEDs due to fewer carriers reaching the sidewall as well as dislocations and point defects. The lateral localization of carriers could also explain the large scattering of the reported size dependencies of micro LEDs.