Pseudo-quaternary GaInAsP semiconductors: A new Ga0.47In0.53As/InP graded gap superlattice and its applications to avalanche photodiodes

We have demonstrated for the first time a pseudo-quaternary GaInAsP semiconductor consisting of a graded gap Ga0.47In0.53As/InP superlattice. The average composition and the band gap of this structure are spatially varied by gradually changing the thicknesses of the InP and Ga0.47In0.53As layers between 5 and 55 Å while keeping constant the period of the superlattice (=60 Å). This new graded gap superlattice has been used to eliminate the interface pile-up effect of holes in a ‘‘high-low’’ InP/Ga0.47In0.53As avalanche photodiode, without requiring the growth of a separately lattice-matched Ga1−xInxAs1−yPy layer. High-speed operation at 1.7 Gb/s and λ=1.55 μm has been achieved. Pseudo-quaternary semiconductors represent a new technique of growing GaInAsP and can conveniently replace conventional Ga1−xInxAs1−yPy alloys in a variety of device applications.