High room-temperature hole concentrations above 10¹⁹ cm^-3 in Mg-doped InGaN/GaN superlattices

We achieved high hole concentrations above 10¹⁹ cm³ at room temperature in Mg-doped In_xGa_1-xN/GaN (4 nm/4 nm) superlattices grown by metalorganic vapor phase epitaxy. The hole concentrations for the In_xGa_1-xN/GaN superlattices increased With the In mole fraction, and the maximum hole concentration reached 2.8 × 10¹⁹ cm^-3 for the In_0.22Ga_0.78N/GaN superlattice. The hole concentrations for the superlattices strongly depend on the structural parameters of the superlattices. The band bending due to the strain-induced piezoelectric field and the valence band structures of the InGaN/GaN heterostructures affect the hole generation in the superlattices. The weak temperature dependence of the resistivities for the InGaN/GaN superlattices With higher In mole fractions indicates highly efficient hole generation in the superlattice.