Measurement of the conduction band discontinuities of InGaAsP/InP heterojunctions using capacitance-voltage analysis.

The relationship between the conduction band discontinuity ((Delta)E(c)) and the band gap difference ((Delta)E(g)) of InGaAsP/InP heterojunctions is measured using capacitance-voltage analysis. It is found that: (Delta)E(c) = (0.39 +- 0.01)(Delta)E (g) over the entire spectrum of compositions of InGaAsP lattice- matched to InP. This result is to be contrasted with those obtained for the GaAs/GaAlAs material system, where 60% - 70% of the band gap difference between a particular composition of GaAlAs and GaAs appears in the conduction band. The measurements discussed in this work were made using novel organic-on-inorganic contact barrier devices. Due to the relatively high energy barriers between certain organic materials and InGaAsP, high resolution measurements of the carrier concentrations, layer thicknesses, conduction band discontinuities, and other relevant parameters were made possible. Wafer contour maps of the fixed charge density (sigma) at the heterointerface constructed using this technique indicate no systematic dependence of (Delta)E (c) on sigma for sigma 5 x 10(10)cm(-2), as expected. Errors incurred with this measurement technique are discussed.