Determination of the valence-band offset and its temperature dependence inisotypic heterojunctions p-AlxGa1-xAs/p-AlyGa1-yAs from C-V measurements

The isotypic heterojunctions p-AlxGa1-xAs/p-AlyGa1-yAs, grown by MOVPE on n -GaAs substrates, have been investigated by the voltage-capacitance method at temperatures ranging from 300 to 100 K. To determine the valence-band of fset Delta E-V and the built-in charge in the heterojunction, the Poisson e quation was solved numerically on a nonuniform coordinate grid. The incompl ete ionization of the acceptors and the different magnitude of the permitti vity in different layers of the heterostructure were taken into account in the calculation. It was found that for a p-Al0.2Ga0.8As/p-Al0.5Ga0.5As hete rojunction Delta E-V at room temperature is 39% (113 meV) of the total gap Delta E-g and decreases monotonically to 35% at T=120 K. (C) 1999 American Institute of Physics. [S1063-7826(99)01108-4].