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

Abstract

The relationship between the conduction band discontinuity (ΔE_c) and the band gap difference (ΔE_g) of InGaAsP/InP heterojunctions is measured for the first time using capacitance–voltage analysis. It is found that ΔE_c=(0.39±0.01)ΔE_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 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. Constructing wafer contour maps of the fixed charge density at the heterointerface (σ) using this technique indicated no systematic dependence of ΔE_c on σ for σ−², as expected.