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We report on the structural, electrical, and optical characterization of GaN epitaxial layers grown by metalorganic chemical vapor deposition (MOCVD) on SiN x and TiN x porous templates in order to reduce the density of extended defects. Observations by transmission electron microscopy (TEM) indicate an order of magnitude reduction in the dislocation density in GaN layers grown on TiN x and SiN x networks (down to ~10 8 cm -2 ) compared with the control GaN layers. Both SiN x and TiN x porous network structures are found to be effective in blocking the threading dislocation from penetrating into the upper layer. Supporting these findings are the results from X-Ray diffraction and low temperature photoluminescence (PL) measurements. The linewidth of the asymmetric X-Ray diffraction (XRD) (1012) peak decreases considerably for the layers grown with the use of SiN x and TiN x layers, which generally suggests the reduction of edge and mixed threading dislocations. In general, further improvement is observed with the addition of a second SiN x layer. The room temperature decay times obtained from biexponential fits to time-resolved photoluminescence (TRPL) data are increased with the inclusion of SiN x and TiN x layers. TRPL results suggest that primarily point-defect and impurity-related nonradiative centers are responsible for reducing the lifetime. The carrier lifetime of 1.86 ns measured for a TiN x network sample is slightly longer than that for a 200 µm-thick high quality freestanding GaN. Results on samples grown by a new technique called crack-assisted lateral overgrowth, which combines in situ deposition of SiN x mask and conventional lateral overgrowth, are also reported.

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The sections in this article are A Device Physics Primer Model Device Structures Semiconductor Materials Used Performance Characteristics of Visible Light Emitting Diodes Infrared Light Emitting Diodes Conclusions Acknowledgments

Si3N4/GaAs metal-insulator-semiconductor (MIS) interfaces with Si(10A)/ Alo 3Gao.TAS (20A) interface control layers have been characterized using capacitance-voltage (C-V) and conductance methods. The structure was in situ grown by a combination of molecular beam epitaxy and chemical vapor deposition. A density of interface states in the 1.1 x 10 '1 eV -1 cm -2 range near the GaAs midgap as determined by the conductance loss has been attained with an ex situ solid phase annealing of 600~ in N 2 ambient. A dip quasi-static C-V demonstrating the inversion of the minority-carrier verifies the decent interface quality of GaAs MIS interface. The hysteresis and frequency dispersion of the MIS capacitors were lower than 100 mV, some of them as low as 50 mV under a field swing of about +2 MV/cm. The increase of the conductance loss at higher frequencies was observed when employing the surface potential toward conduction band edge, suggesting the dominance of faster traps. Self-aligned gate depletion mode GaAs metal-insulator-semiconductor field-effect transistors with Si/A103Gao7As interlayers having 3 ~tm gate lengths exhibited a transconductance of about 114 mS/ram. The present article reports the first application of pseudomorphic Si/ Alo ~Gao.r~ interlayers to ideal GaAs MIS devices and demonstrates a favorable interface stability.