Migration enhanced lateral epitaxial overgrowth of AlN and AlGaN for high reliability deep ultraviolet light emitting diodes

Abstract

We report on the growth of low-defect thick films of AlN and AlGaN on trenched AlGaN/sapphire templates using migration enhanced lateral epitaxial overgrowth. Incoherent coalescence-related defects were alleviated by controlling the tilt angle of growth fronts and by allowing Al adatoms sufficient residence time to incorporate at the most energetically favorable lattice sites. Deep ultraviolet light emitting diode structures $\left(310\mathrm{nm}\right)$ deposited over fully coalesced thick AlN films exhibited cw output power of $1.6\mathrm{mW}$ at $50\mathrm{mA}$ current with extrapolated lifetime in excess of $5000\text{hours}$ . The results demonstrate substantial improvement in the device lifetime, primarily due to the reduced density of growth defects.