Papers by Keyword: Threading Dislocation Density

Abstract: Blue light-emitting diodes (LEDs) with an InGaN multi-quantum well (MQW) structure were fabricated on cone-shaped patterned sapphire substrate (PSS) using a single growth process of metal organic chemical vapor deposition (MOCVD). The PSS was proved to be an efficient method to decrease the threading dislocation (TD) density in GaN epifilm with the lateral growth mode on PSS. The LED designed on PSS increased the electroluminescene (EL) intensity. The internal quantum efficiency is increased by reducing the dislocation density, and light extraction efficiency is also enhanced owing to PSS.

Abstract: Germanium-rich silicon-germanium (Si_1-xGe_x: 0.98≤x≤1) films were epitaxially grown on Si (001) substrate by reactive thermal chemical vapor deposition at low temperature. Si₂H₆ and GeF₄ were used as source gases. The effect of gas flow ratio between Si₂H₆ and GeF₄ was studied to optimize the film quality. The results indicated that Si_1-xGe_x (x≥0.99) epilayer can be prepared directly on Si wafer at 350°C with a threading dislocation density of ~7×10⁵/cm² and surface RMS roughness of 1.0 nm. Hall-effect and conductivity measurements revealed that the epilayer was p-type conduction with the hall mobility of 767 cm²/Vs and the hole concentration of 6.08×10¹⁶/cm³. Those results indicated the Ge-rich Si_1-xGe_x was an excellent candidate for bottom cells of multijunction solar cells.

Abstract: The impact of threading dislocation density on the leakage current of reverse IV characteristics in 1.2 kV Schottky barrier diodes (SBDs), junction barrier Schottky diodes (JBSDs), and PN junction diodes (PNDs) was investigated. The leakage current density and threading dislocation density have different positive correlations in each type of diode. For example, the correlation in SBDs is strong, but weak in PNDs. The threading dislocations were found to be in the same location as the current leakage points in the SBDs, but not in the PNDs. Nano-scale inverted cone pits were observed at the Schottky junction interface in SBDs, and it was found that leakage current increases in these diodes due to the concentration of electric fields at the peaks of the pits. These nano-scale pits were also observed directly above threading dislocations. In addition, this study succeeded in reducing the leakage current variation of 200 A-class JBSDs and SBDs by eliminating the nano-scale pits above the threading dislocations. As a result, a theoretical straight-line waveform was achieved.