Epitaxial Growth of GaN by Helicon Wave Plasma Assisted Metal Organic Chemical Vapor Deposition Process

Abstract

A high density helicon wave plasma (HWP) source was used to synthesize a thin film of GaN epilayer on sapphire (0001). The plasma source coupled with RF field was diagnosed with the aid of an electrical probe and an ion energy analyzer in order to investigate its applicability to the epitaxial film growth process. The helicon wave excited plasma produced by Ar+N2 mixed gases was extensively investigated to enhance activated nitrogens while simultaneously reducing their ion energy for their utilization in the synthesis of GaN film with the help of a TMGa precursor. By controlling the mixing ratio of Ar to N2 gases, the optimum plasma conditions suitable for growing the GaN epilayer were determined to be as follows: ratio of Ar to total (Ar+N2) gas flow \\cong0.5, RF power of 400 W and axial magnetic field of 750 G. The GaN films synthesized by the HWP-assisted MOCVD process under optimum deposition conditions featured good crystallinity, and showed a full width of half maximum (FWHM) of 6.5 arcmin for the GaN (002) peak rocking curve. The effects of deposition temperature, group III/V elemental ratio and plasma conditions on the crystalline quality of the film are discussed.