Limitations on stress compensation in AlxGa1 −xAs1−yPy–GaAs LPE layers

It has been shown previously that the room-temperature lattice mismatch between GaAs and AlxGa1−xAs may be reduced by the incorporation of small amounts of phosphorus in the alloy. By measuring the curvature of thin (2 μ) freely suspended foils of AlxGa1−xAs1−yPy grown by LPE, we have determined the gradient in the lattice parameter in foils which have been substantially stress-compensated. This gradient is caused by depletion of aluminum and phosphorus from the melt during growth. Such depletion limits the extent to which this stress-compensating technique may be applied to the growth of GaAs heterostructure lasers. Present results imply that stress reductions of about a factor of 10 may be obtained for 2-μ quaternary layers, although greater factors are achievable for thinner layers.