Ultrahigh luminescence extraction via the monolithic integration of a light emitting active region with a semiconductor hemisphere

A light emitting active region with three InGaAs quantum wells is monolithically integrated with a GaAs hemisphere as a means to increase the extraction efficiency of light emitting diodes. For a device with a small active region and large hemisphere and optimal antireflection, theoretical calculations show that the extracted fraction of spontaneous emission incident on the hemisphere is greater than 99.9% and the overall extraction efficiency of the integrated device is as high as 90%. The hemisphere is fabricated with a consistent aspect ratio (height versus width) using photoresist reflow and inductive coupled plasma etching. Detailed numerical simulations are performed to predict the reflow and dry etch processes as an aid to device fabrication. The fabrication results show that near perfect GaAs hemispheres can be successfully integrated with light emitting active regions and that the resulting light emitting diodes have the potential for mass production.