Pseudomorphic Semiconducting Heterostructures from Combinations of AlN, GaN and Selected SiC Polytypes: Theoretical Advancement and Its Coordination with Experimental Studies of Nucleation, Growth, Characterization and Device Development

As an initial step toward the achievement of pseudomorphic heterostructures of nitride materials, thin films of an undoped and p-type doped AIxGal-xN solid solution as well as InN have been successfully deposited using a modified gas source MBE system. Application of single layers of the AlxGal-xN solid solution or pure GaN films as UV light photon detectors has been achieved. The gain exhibited by these detectors at a forward voltage of 5V was 500uA and 10 mA for the solid solution films deposited on sapphire and alpha6H-SiC substrates, respectively. The GaN film deposited on sapphire exhibited a gain of 20uA. Solid solutions and multilayers of AIN and SiC have also been grown on 6H- SiC 0001 substrates cut 3-4 deg off-axis to 1120. Evidence is presented which suggests that the AIN-rich solid solutions are cubic. Pseudomorphic heterostructures of 6H-SiC, 2H-AIN, and 3C-SiC have been produced for the first time. Each of the layers was monocrystalline, and the interfaces were chemically and structurally sharp and reasonably smooth. Moreover, each layer represents a different crystal structure and bandgap energy. In concert with this research, we are also investigating the chemical interdiffusion of AIN and SiC. Initial results indicate that the interdiffusivity of the four elements is approx. 10-14 cm2hr. Finally, initial research concerned with the BN on polycrystalline CVD diamond is reported.