Characterization of the properties of Mg-doped Al_0.15Ga_0.85N/GaN superlattices

Low resistivity Mg-doped Al_0.15Ga_0.85N/GaN strained-layer superlattices (SLs) were grown. In these SLs, the maximum hole concentration is 3 × 10¹⁸cm^-3 at room temperature, i.e., larger than those for Mg-doped Al_0.15Ga_0.85N and GaN bulk layers with the same Cp₂Mg flow rates during growth. Hall effect measurements indicate high conductivity of this structure in which the high activation efficiency is attributed to the strain-induced piezoelectric fields. In addition, photoluminescence measurements revealed a blue band at 2.9 eV in Mg-doped Al_0.15Ga_0.85N/GaN SLs, which could be attributed to a distant donor-to-acceptor transition feature. This work also fabricated InGaN/GaN blue light emitting diodes (LEDs) that consist of a Mg-doped Al_0.15Ga_0.85N/GaN SLs. Experimental results indicate that the LEDs can achieve a lower operation voltage of around 3 V, i.e., smaller than conventional devices which have an operation voltage of about 3.8 V.