30-mW-Class High-Power and High-Efficiency Blue Semipolar (10\bar1\bar1) InGaN/GaN Light-Emitting Diodes Obtained by Backside Roughening Technique

The first 30-mW-class semipolar blue light-emitting diode (LED) on a free-standing (1011) GaN substrate has been demonstrated by using microscale periodic backside structures. The light extraction efficiency and corresponding output power were greatly enhanced, by up to 2.8-fold (bare chip) compare with conventional devices. At a driving current of 20 mA, the LED showed an output power of 31.1 mW and an external quantum efficiency of 54.7%. Semipolar GaN LED technology is now comparable to commercial c-plane blue LED technology, not only in terms of internal material properties but also in terms of chip processing techniques.