Growth and fabrication of AlGaN-based ultraviolet light emitting diodes on 6H-SiC(0 0 0 1) substrates and the effect of carrier-blocking layers on their emission characteristics

• Published in: Materials science & engineering. B, Solid-state materials for advanced technology Vol. 127; no. 2; pp. 169 - 179
• Main Authors: Park, Ji-Soo, Reitmeier, Zachary J., Fothergill, Daryl, Zhang, Xiyao, Muth, John F., Davis, Robert F.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25.02.2006
• Subjects: AlGaN; Carrier-blocking layers; Light emitting diodes; Ultraviolet; Light emitting diodes; Carrier-blocking layers; Ultraviolet; AlGaN
• ISSN: 0921-5107; 1873-4944
• DOI: 10.1016/j.mseb.2005.10.019

Growth, fabrication, and the electrical and optical characterization of ultraviolet light emitting diodes and their components, including Al x Ga 1− x N films, quantum wells (QWs), and ohmic contacts, and the problems encountered in the process integration of these components have been investigated. Ni/Au ohmic contacts with specific contact resistivities of 2.2 × 10 −4 and 2.0 × 10 −2 Ω cm 2 were achieved on annealed, Mg-doped ([Mg] ∼ 5 × 10 19 cm −3), p-type GaN layers that had been cleaned in HCl at 85 °C and on the backside of the SiC substrates after annealing in nitrogen, respectively. The emission intensity of the diodes increased with an increase in the number of Al 0.06Ga 0.94N/Al 0.10Ga 0.90N QWs and with the use of Si-doped n-type barrier layers. The highest intensities of the principle emission at 353 nm were measured at all values of the injection current in the device with a p-type carrier-blocking layer at the top of the QWs; this device also exhibited the highest values of light output power. Growth of an n-type carrier-blocking layer at the bottom of the QWs had an adverse effect on their characteristics. A broad peak centered at ∼540 nm exhibited yellow luminescence and was present in the spectra acquired from all the devices. This peak is attributed to absorption of the ultraviolet emission by and re-emission from the p-GaN and/or to the luminescence from the AlGaN within QWs by current injection.