Strain effects in GaN/AlN short‐period superlattices for intersubband optoelectronics

In this work we report on the strain relaxation processes in GaN/AlN short-period superlattices (SLs) displaying intersubband transitions at 1.55 μm. The growth process was tuned to minimize the strain relaxation in the superlattices either by plastic or elastic channels. X-ray diffraction measurements show that the SL final strain state is substrate independent. The relaxation path followed by the SLs was traced in situ with reflection high-energy electron diffraction, which reveals an initial transient strain state of about 12 periods to accommodate the lattice mismatch. Once steady-state conditions are attained, we observe a periodic relaxation process with generation of misfit dislocations at the GaN/AlN interface. The relaxation process in the SLs has been confirmed by various characterization tools. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)