Growth and characterization of a high-quality Al0.45Ga0.55N layer with AlGaN/AlN superlattices

We report the growth and characterization of a Si-doped, n-type AlGaN layer with 45% Al composition. For the application of n-type AlGaN layers with high Al compositions in ultraviolet emitters, we fabricated an n-Al0.45Ga0.55N layer with high crystalline quality and high electrical conductivity by inserting Al0.85Ga0.15N/AlN superlattices (SLs) to prevent cracks prior to growing the n-type AlGaN layer. The dislocation density in the n-AlGaN layer with a 45% Al composition and SLs was less than 2.4 x 10(10) cm(-2), which was lower than the dislocation density of 5.3 x 10(10) cm(-2) for the n-AlGaN layer without SLs. The resistivity, mobility, and free-electron concentration in the n-type Al0.45Ga0.55N layer with SLs were 2.2 x 10(-2) Omega center dot cm, 55.0 cm(2)/V-s, and 5.0 x 10(18) cm(-3) at room temperature, respectively.