Determination of the valence band offset of MOVPE-grown In0.48 Ga0.52 P/GaAs multiple quantum wells by admittance spectroscopy

The valence band discontinuity of the lattice matched In0.48Ga0.52P/GaAs heterostructure was determined through a careful analysis of the temperature and frequency dependence of the admittance of p+ /MQW/n+ structures, formed by a nominally undoped InGaP/GaAs multiple quantum well region, interposed between p+ and n+ GaAs layers. The heterostructures were grown through metal organic vapor phase epitaxy by using tertiary butyl arsine and tertiary butyl phosphine as alternative precursors for the V-group elements. The growth conditions were optimized for obtaining sharp interfaces and negligible ordering effects in the cation sublattice. Accounting for the temperature dependence of the Fermi energy and the calculated confining energy 10 meV of the heavy holes in the wells, a valence band offset EV= 356 5 meV was derived from the temperature variation of the resonance frequency at which the isothermal conductance over frequency G / curves show a maximum. The experimental uncertainty of this result is significantly low if compared with the wide range 240– 400 meV of the previously reported EV values. By considering the band gap difference between InGaP and GaAs, a conduction band offset EC= 119 meV was estimated. The accuracy of the experimental procedure and the reliability of the main assumptions of the admittance spectroscopy measurements were accurately checked. The obtained results were discussed in light of the large and growing amount of literature data by taking into account the influence of the growth conditions on the physical properties of the InGaP/GaAs quantum wells.