structure a aln gan aln quantum well structure or a al in ga n gan al in ga n quantum well structure the al in ga n ingan sl superlattice layer may be a al in ga n ingan 2 nm 2 nm superlattice or a al in ga n ingan x nm y nm superlattice the al in ga n ingan sl superlattice layer may be a p type doped layer or a non doped layer the p al in ga n layer is a binary alloy layer of p gan p inn or p aln or a ternary alloy layer of p algan p alinn or p ingan or a quaternary alloy layer of alingan the substrate may be a silicon substrate a sic substrate a sapphire substrate or a homo epitaxial gan substrate fig2 a and fig2 b are schematic diagrams for dry etching a p type al in ga n layer in a region excluding the gate as shown in fig1 by shielding with a gate mask the p type al in ga n layer in the region excluding the gate may be dry etched with cl based plasma cl 2 bcl 3 fig2 a until reaching the al in ga n ingan superlattice stopping layer fig2 b fig3 shows comparison of energy band diagrams.