A systematic study will be performed on the structural optimization of GaAs-based and InP-basedstrained resonant tunneling devices. The two additional variables which result from using the strained layers, namely the lattice strain and the band gap, will be considered in designing the structure. The I-V characteristics and tunneling escape times will be calculated using available theoretical methods such as, for example, the Airy function approach. Theoretical results are expressed in terms of the barrier height & thickness and well depth thickness. Based on the simulation results, device structures will be grown by metalorganic chemical vapor deposition or by molecular beam epitaxy. Tunneling diodes will be fabricated and characterized. Correlation studies will be made of the device performance characteristics with the various theoretical simulation results and the structural characteristics such as interface roughness, lattice strain, interface mismatch, and layer thicknesses compositions . Nondestructive structural characterization will be performed by the x-ray rocking curve (XRC), photoluminescence (PL), and photoreflectance (PR) techniques.