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Article Dans Une Revue Journal of Applied Physics Année : 2009

Strain relaxation in short-period polar GaN/AIN superlattices

Résumé

We have investigated the strain relaxation mechanisms in short-period polar GaN/AlN superlattices deposited by plasma-assisted molecular-beam epitaxy, and designed to display intersubband transitions at 1.55 µm. In a first stage, we have identified the growth conditions to minimize strain relaxation, using a Ga excess to reduce the (0001) surface free energy of both GaN and AlN. Under these growth conditions, crack propagation is not observed, even for the tensile-strained superlattices grown on GaN templates. The initial misfit relaxation in the vicinity of the buffer occurs by the formation of a-type dislocations. The final strain state of the superlattice, reached after 10–20 periods, is independent of the substrate (either GaN or AlN templates). Once the steady-state conditions are reached, we observe a periodic partial relaxation of quantum wells and barriers. High-resolution transmission electron microscopy indicates that the periodic relaxation can be related to the presence of basal and prismatic stacking faults creating clusters with an in-plane length of tens of nanometers. The effect of these defects on the optical performance of the superlattices is discussed by simulation of electronic structure using an 8x8 k• p Schrödinger–Poisson solver. In the presence of basal stacking faults at the quantum well interfaces, the deviation of the e1-e2 intersubband transition with respect to the nominal value is expected to be smaller than the measured absorption line width.
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Dates et versions

hal-00438189 , version 1 (02-12-2009)

Identifiants

Citer

P. K. Kandaswamy, Catherine Bougerol, D. Jalabert, Pierre Ruterana, E. Monroy. Strain relaxation in short-period polar GaN/AIN superlattices. Journal of Applied Physics, 2009, 106 (1), pp.013526. ⟨10.1063/1.3168431⟩. ⟨hal-00438189⟩
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