Caracterização de semicondutores III-V : descontinuidades de bandas e poços quanticos

AUTOR(ES)
DATA DE PUBLICAÇÃO

1991

RESUMO

In this work, we present a systematic study of two properties of III-V compounds heterostructures which are of great interest to Semiconductor and Device Physics: band offsets in isotype heterojunctions (HJs) grown by LPE and optical properties of MOVPE grown quantum wells. Using for the first time the technique of electrochemical C-V profiling, we measured the conduction band discontinuities (DEc) in HJs and determined the ratio between D Ec and DEg, the difference between the two HJs band gaps. We found DEc/DEg to be 0.6 in Ga1-xAlxAs/Ga1-yAlyAs, for x between 0 and 0.21, keeping y around 0.42. These are the first results in samples where the composition of the smaller band gap layer was varied. We also found DEc/DEg to be 0.36 for In0.59Ga0.47As/InP. We also characterized MOVPE grown GaAlAs/GaAs quantum wells by photoluminescence at 77K, varying the confining barrier height, and developed a method for determining interface grading in such heterostructures. Using the envelope function approximation. We calculated theoretical curves Wavelength versus Well Width (l x Lz) corresponding to the recombination between the lowest energy levels in an ideally perfect well. The departure of the experimental curves from the theoretical one allowed us to determine the interface grading that best describes the experimental points. Calculations were made by solving the Schroedinger equation by simple numerical methods. Grading determination was shown to increase with the Al content in the barrier. The method is very precise, limited only by the uncertainty in the growth rate. InGaAs/InP and InGaAs/InGaAlAs wells were also investigated and the latter had been shown more efficient because the former involves difficulties in hydride changes at the interfaces. An extension of this method was successfully applied to the study of Ga-In disorder in InGaAs/GaAs pseudomorphic structures, enhanced by Zn doping and heat treatment In-Ga interdiffusion coefficients for different Zn diffusion conditions were determined using this characterization method

ASSUNTO(S)

semicondutores fisica do estado solido

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