Analysis of a Phase Factor of Franz-Keldysh Oscillations in GaAs/AlGaAs Heterostructures(<Special Issue>Heterostructure Microelectronics with TWHM2003)

概要

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We propose an analysis method for Franz-Keldysh (FK) oscillations appearing in photoreflectance (PR) spectra of heterojunction device structures, which enables precise and simultaneous evaluation of the built-in electric field strength and band-gap energy. Samples for PR measurements were n^+-GaAs/n-Al_<0.3>Gao_<0.7> As/i-GaAs heterostructures with different Al_<0.3>Ga_<0.7>As-layer thickness. We have found that the phase of the EK oscillations originating from the i-GaAs buffer layer depends on the Al_<0.3>Gao_<0.7> As-layer thickness. We have derived a calculation model for FK oscillations that includes the interference of probe light. From the comparison of the calculated spectra with the measured spectra, we conclude that mixing of the real and imaginary parts of a modulated dielectric function, which is caused by the probe-light interference, gives rise to the phase shift of the FK oscillations. Our FK-oscillation analysis method reduces ambiguity in the estimation of band-gap energy that is considerable in a conventional analysis.
社団法人電子情報通信学会の論文
2003-10-01