Effect of dimethylhydrazine on p-type conductivity of as-grown Mg-doped GaN

Mg dopants in GaN need post‐growth thermal activation to be activated. However, it was observed that GaN grown with dimethylhydrazine (DMHy) resulted in p‐type conductivity without activation. The reduction of NH3 flow by adding DMHy resulted in a very low hydrogen concentration of 2.8 × 1017 cm–3 in Mg‐doped GaN, which was even lower than the hole concentration. The low‐temperature infrared transmittance spectra also showed that many hydrogen atoms were captured by incorporated carbon impurities. The combined effect of low concentration of hydrogen and the preferred trapping of hydrogen at carbon impurities is attributed to the p‐type conductivity of as‐grown Mg‐doped GaN when a mixture of DMHy and NH3 was used for group V sources. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) This Letter explains the reason why Mg‐doped GaN epilayers grown with a dimethylhydrazine (DMHy)/NH3 mixture have p‐type conductivity without thermal activation. An addition of DMHy substantially decreases the amount of incorporated hydrogen in GaN, minimizing Mg acceptor passivation by hydrogen.