RESUMEN
In this study, we demonstrated the defect-selective etching and epitaxy technique for defect reduction of a heteroepitaxial chemical vapor deposition (CVD) diamond substrate. First, an 8 nm layer of nickel was deposited on the diamond surface using an e-beam evaporator. Then, defect-selective etching was conducted through an in situ single process using microwave plasma chemical vapor deposition (MPCVD). After defect-selective etching, the diamond layer was overgrown by MPCVD. The defect density measured from the atomic force microscope image decreased from 3.27×108 to 2.02×108 cm-2. The first-order Raman peak of diamond shifted from 1340 to 1336 cm-1, and the full width at half maximum (FWHM) decreased from 9.66 to 7.66 cm-1. Through the defect-selective etching and epitaxy technique, it was confirmed that the compressive stress was reduced and the crystal quality improved.
RESUMEN
A DUV-LED with a graded superlattice electron blocking layer (GSL-EBL) is demonstrated to show improved carrier injection into the multi-quantum well region. The structures of modified EBLs are designed via simulation. The simulation results show the carrier behavior mechanism of DUV-LEDs with a single EBL (S-EBL), graded EBL (G-EBL), and GSL-EBL. The variation in the energy band diagram around the EBL region indicates that the introduction of GSL-EBL is very effective in enhancing carrier injection. Besides, all DUV-LEDs emitting at 280 nm are grown in the high temperature metal organic chemical deposition system. It is confirmed that the optical power of the DUV-LED with the GSL-EBL is significantly higher than that of the DUV-LED with the S-EBL and G-EBL.