Schottky contacts and conduction band offsets in bandgap engineered InGaAlAs/InP heterostructures

The I-V/C-V characteristics of Schottky diodes fabricated on InGaAlAs/InP heterostructures are reported with Al mole fraction varying in the quaternary alloy. InGaAlAs epilayers are grown lattice-matched to InP by molecular beam epitaxy with bandgap varying in the energy range 0.8-1.42 eV. It is noted that at room temperature the Schottky characteristics are not observable on these structures where the Al mole fraction is less than 0.42 because of the low metal-semiconductor contact potentials and the dominance of thermionic emission. CV measurement is found to be appropriate for determining the conduction band offsets in samples where the contact is ohmic. This occurs for the case where Al mole fraction is less than 0.12. Also noted is that for an Al mole fraction of 0.23, the bandgap lineup changes from type I to staggered type Il. The variation of Schottky barrier potential is also reported as a function of Al mole fraction in the alloy