Mg-doped green light emitting diodes over cubic (111) MgAl2O4 substrates

We report on the fabrication and characterization of Mg-doped green light emitting diodes (LEDs) over cubic (111) MgAl${}_2$ O${}_4$ substrates with a very strong impurity band electroluminescence. A 0.2-micron-thick Mg-doped In${}_{\text{0.13}}$ Ga${}_{\text{0.87}}$ N layer was used in the active region of mesa type LED structures. The emission spectrum was centered at 510 nm (green) with a full-width at half-maximum of 60 nm. At a forward bias current of 20 mA the output power and the external quantum efficiency were about 200 $\mu$ W and 0.3%. The origin of green light in the Mg-doped In${}_{\text{0.13}}$ Ga${}_{\text{0.87}}$ N layer has also been studied by time resolved photoluminescence. Our study demonstrates impurity band LEDs to be a viable alternative to band edge emission green LEDs with high indium mole fractions in the active region.