Characteristics of Si-doped GaN compensated with Mg

We have investigated the effect of Si-Mg codoping on the yellow luminescence. The codoped GaN films with GaN buffer layers were grown by introducing various SiH₄ flow rates (2-10 seem) and constant Cp₂Mg flow rate (3 sccm) at the same time. All the codoped GaN epilayers measured by Hall effect were n-type, leading to electron concentration from 2 × 10¹⁸ up to 5 × 10¹⁹ cm^-3. From the photoluminescence spectra, the integrated intensity ratio of the yellow luminescence to the band-edge emission of the codoped GaN samples is lower than that of the GaN samples doped with the Si donors alone, regardless of the electron concentration and the measuring temperature. We interpret that the Ga vacancy (V_Ga) is responsible for the yellow luminescence.