Topography of (202¯1) AlGaN, GaN and InGaN layers grown by metal-organic vapor phase epitaxy

► Semipolar (202¯1) AlGaN, GaN and InGaN layers were grown on (202¯1) GaN substrates by MOVPE. ► Undulations along [101¯4] were observed in all layers. ► A model to explain the undulations was developed and exhibits (101¯1) and (101¯0) microfacets to be the origin. ► TEM images confirm that 50 nm long (101¯1) and (101¯0) microfacets to be very stable. ► Growth condition for smooth (202¯1) GaN layers with rms roughness <0.4nm has been established.