Enhanced vertical and lateral hole transport in high aluminum-containing AlGaN for deep-UV light emitters

We report improved p-type conductivity in AlGaN:Mg superlattice (SL) cladding layers designed for deep ultraviolet light emitting devices operating at wavelengths down to 255 nm. The average Al composition in the SL was about 60%. Up to 2.1 amperes (equivalent to a current density of 21 kA/cm2) was injected vertically (perpendicular to the growth plane) through the p-type SL. The measured vertical conductivity of 6.6x10-5 S/cm in the SL is about two times greater than the conductivity of homogeneous p-Al0.6Ga0.4N. The conductivity in the lateral direction (parallel to the growth plane) was also enhanced. We attribute the improved conductivity obtained with the SL to polarization-field assisted doping. The effective acceptor activation energy in the SL was determined to be 17 meV, nearly one order of magnitude less than the acceptor activation energy in homogeneous p-type GaN.

Citation

Cheng, B.; Choi, S.; Northrup, J. E.; Yang, Z.; Knollenberg, C.; Teepe, M. R.; Wunderer, T.; Chua, C. L.; Johnson, N. M. Enhanced vertical and lateral hole transport in high aluminum-containing AlGaN for deep-UV light emitters. Applied Physics Letters. 2013; 102 (23): 231106.