Effects of film polarities on InN growth by molecular-beam epitaxy

Effects of the film polarity on InN growth were investigated in molecular-beam epitaxy (MBE). It was found that N-polarity InN could be grown at higher temperatures than In-polarity one. For the In-polarity films, which were grown on Ga-polar GaN template, the highest growth temperature was limited below $\text{500\hspace{0.05em}°}\mathrm{C},$ and the surface morphology and crystal quality tended to be poor mainly because of the tolerated low growth temperature. While for the N-polarity InN films, which were grown on MBE-grown N-polar GaN, the growth temperature could be as high as $\text{600\hspace{0.05em}°}\mathrm{C}.$ The step-flow-like growth morphology was achieved for the InN films grown with N polarity at $\text{580\hspace{0.05em}°}\mathrm{C}.$ The resulting full widths of half maximum of x-ray rocking curve around InN (002) and (102) reflections were about 200–250 and 950–1100 arc sec, respectively. The photoluminescence of the InN films peaked at 0.697 eV. The recording Hall mobility of InN film grown in N polarity is $\text{1400\hspace{0.17em}}{\mathrm{cm}}^2/\mathrm{V s}$ with a background carrier concentration of ${\text{1.56×10}}^{18}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}$ at room temperature. For both-polarity films, we found N-rich condition was necessary for the stable InN growth.