Layer-structured hexagonal (BN)C semiconductor alloys with tunable optical and electrical properties

Hexagonal boron nitride carbon, h(BN)1-x(C2)x, semiconductor alloys have been grown on sapphire substrates by metal-organic chemical vapor deposition. Bandgap tuning through compositional variation has been demonstrated via optical absorption measurements. Furthermore, an enhancement of approximately 10 orders of magnitude in the electrical conductivity has been attained by increasing the carbon concentration (x) from 0 to 0.21. Experimental results revealed evidences that the critical carbon concentration xc to form the homogenous h(BN)1-x(C2)x alloys, or the carbon solubility in hBN is about 3.2% at a growth temperature of 1300 C before carbon clusters form. Based on the predicted phase diagram of cubic (BN)1-x(C2)x and the excellent matches in the structural and thermal properties of hBN and graphite, it is expected that homogenous h(BN)1-x(C2)x alloys with higher x can be achieved and the alloy miscibility gap can be reduced or completely removed by increasing the growth temperature. This is a huge advantage over the InGaN alloy system in which InN decomposes at high temperatures and high growth temperature cannot be utilized to close the miscibility gap. The results indicate that the h(BN)1-x(C2)x alloy system has the potential to tackle the challenging issues facing the emerging two-dimension materials beyond graphene, which include realizing the bandgap engineering, conductivity control, and large wafers of homogeneous films. VC 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4867641]