Pulsed modulation doping of AlxGa1‐xN (x>0.6) AlGaN epilayers for deep UV optoelectronic devices

Abstract

AbstractWe report a new approach of pulsed modulation doping (PMD) to achieve n‐type doping in AlxGa1‐xN (x>0.6) layers. In this approach silane flow is cyclically modulated during n‐AlGaN growth which enable us to grow low dislocation density n‐AlGaN templates for UV (λ ∼ 280 nm) LEDs. We observed that dislocation density for un‐doped AlGaN layers on high quality AlN layers is 3.3×108cm‐2. This dislocation density was increased to 2.3×109 cm–2 for conventionally grown n‐AlGaN layers on AlGaN templates. We were able to reduced dislocation density in n‐AlGaN layers to 3.5×108cm–2 using PMD of n‐AlGaN layers. The dislocation densities in these samples were studies using etch pit density (EPD) and Williamson and Hall studies. A comparative study of LED structures on conventional and PMD doped n‐AlGaN showed improved performance for LED emitting at 280 nm for LED structure on PMD n‐doped AlGaN layers. In this paper the details of our growth procedure, the epi‐structure X‐ray, AFM, and other characterizations will be presented. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)