Unintentionally doped semi-insulating GaN with a low dislocation density grown by metalorganic chemical vapor deposition

Unintentionally doped semi-insulating GaN films possessing a low dislocation density are grown via metalorganic vapor phase epitaxy on a sapphire substrate. The obtained electrical resistivity reaches 4.8 × .a8 Ω·cm, and the full width at half maximum of the x-ray diffraction rocking curves of the (002) and (102) planes is as low as 201.6 and 378.0 arcsec, respectively. The GaN films are grown at low pressure (LP) to introduce residual carbon and to compensate background donors. The dislocation density in these samples is significantly reduced by using a low V/III ratio in the initial epitaxial growth stage. It is also found that the resistivity of the LP-grown samples decrease when the residual carbon concentration is excessive, which is attributed to the self-compensation of carbon impurities. Therefore, the carbon concentration of LP-grown GaN should be carefully modulated to maintain its high resistivity.