Germanium doping of GaN by metalorganic chemical vapor deposition for polarization screening applications

Publication date: 1 December 2016
Source:Journal of Crystal Growth, Volume 455
Author(s): N.G. Young, R.M. Farrell, M. Iza, S. Nakamura, S.P. DenBaars, C. Weisbuch, J.S. Speck
We demonstrate n-type doping of GaN with Ge by MOCVD at high concentrations that are necessary to fully screen the polarization fields in c-plane InGaN/GaN quantum wells. Hall measurements show linear Ge incorporation with dopant flow rate and carrier concentrations exceeding 1×10²⁰ cm⁻³. GaN:Ge layers exhibit excellent electron mobility, high conductivity, and contact resistivity comparable to the best unannealed contacts to Si-doped GaN. However, the surface morphology begins to degrade with Ge concentrations above 1×10¹⁹ cm⁻³, resulting in severe step bunching and a network of plateaus and trenches, even in layers as thin as 10nm.