Efficient hole generation above 10¹⁹ cm^-3 in Mg-doped in GaN/GaN superlattices at room temperature

We achieved spatially averaged hole concentrations above 10¹⁹ cm^-3 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 are larger than those for the InGaN bulk layers with the same average In mole fraction. The weak temperature dependence of the resistivities for InGaN/GaN superlattices with higher In mole fractions indicates highly efficient hole generation in the superlattice.