GaN based epitaxy on silicon usually required strain-engineering methods to avoid tensile stress after cooling from growth temperature. Silicon doping of GaN induces additional tensile stress during growth originating from edge dislocation climb. Especially in the GaN-on-Si case high tensile stresses for highly Si-doped layers limit the freedom in device design and performance. It was shown that germanium doping did not influence strain evolution and enabled the growth of thick highly n-type doped crack-free layers on silicon. It was concluded that dislocation climb in the case of silicon doping did not originate from surface roughening but from silicon-nitride induced dislocation masking.

Crack-Free, Highly Conducting GaN Layers on Si Substrates by Ge Doping. A.Dadgar, J.Bläsing, A.Diez, A.Krost: Applied Physics Express, 2011, 4[1], 011001