Characterization of band offset in α-(AlxGa1-x)2O3/ α-Ga2O3 heterostructures
Gallium Oxide is a promising material for power device applications. We focused on corundum structured gallium oxide (α-Ga<sub>2</sub>O<sub>3</sub>) and α-(Al<sub>x</sub>Ga<sub>1-x</sub>)<sub>2</sub>O<sub>3</sub>/ α-Ga<sub>2</sub>O<sub>3</sub> heterostructure devices. We prepared α-(Al<sub>x</sub>Ga<sub>1-x</sub>)<sub>2</sub>O<sub>3</sub> alloy and these laminate structures on c-plane sapphire substrates. The band offset of the α-Ga<sub>2</sub>O<sub>3</sub>/α-(Al<sub>x</sub>Ga<sub>1-x</sub>)<sub>2</sub>O<sub>3</sub> heterostructure was measured by X-ray photoelectron spectroscopy (XPS). The band alignment was estimated to be type I with very narrow valence-band offset energy.
Electronic and thermal properties of wide bandgap materials from density functional theory
Wide bandgap materials, e.g. SiC, GaN, ZnO, Ga2O3, and diamond, find many applications in microelectronics such as high electron mobility transistors (HEMT), field effect transistors, and light-emitting diodes (LED). Great efforts are being made on the wide bandgap materials as mandated by next generation device design and fabrications. This work focuses on three topics: heat transport in SiC/diamond/Si systems, the electronic properties of (AlxGa1−x)2O3 alloys, and phonon-limited electron transport in ZnO and GaN. The computational simulation is based upon the density functional theory (DFT) which provides efficient means to investigate a system from a quantum mechanics description and has become a powerful tool in computational materials science. This work uses a combined approach of DFT, density functional perturbation theory (DFPT), classical heat diffusion models, and special quasirandom structures (SQS) models. Heat transport is critical in diamond/Si/SiC system for advanced applications in high energy laser (HEL) mirrors and semiconductor devices. We calculated the relations between the effective thermal conductivity and grain size in polycrystalline diamond. We also derived thermal barrier resistances in Si/diamond, Si/SiC, SiC/diamond, and GaN/diamond heterostructures which are important parameters in developing relevent composites and simulating device performances. (AlxGa1−x)2O3 alloys are promising materials for solar-blind UV photodetectors and high-power transistors. From hybrid-functional calculations, we computed formation enthalpies, band gaps, and band edge positions of (AlxGa1−x)2O3 alloys. We found the formation enthalpies of (AlxGa1−x)2O3 alloys are relatively low and that (AlxGa1−x)2O3 with x=0.5 can be considered as an ordered compound AlGaO3 in the
17 &mgr;m pixel 640 x 480 microbolometer FPA development at BAE Systems
BAE Systems has developed an advanced 640 x 480 focal plane array (FPA) with a 17 &mgr;m pixel pitch. Sensitivity of ≤ 50 mK was demonstrated and the FPAs were used in imaging demonstrations. Successful scaling of BAE Systems' patented single contact per pixel, single-level microbolometer process to 17 &mgr;m pitch provides a path toward next generation microbolometer imaging systems.