Control of Order Parameter during Growth of In0.5Ga0.5P/GaAs Heterostructures by Gas Source Molecular Beam Epitaxy Using Tertiarybutylphosphine

Abstract

For the <001>-oriented In0.5Ga0.5P/GaAs heterostructure grown by gas source molecular beam epitaxy (GSMBE) using tertiarybutylphosphine (TBP), presence of the natural ordering of group III atoms and its effect on heterointerface properties are investigated for the first time. Using in situ reflection high energy electron diffraction (RHEED) observation and photoluminescence (PL) measurements, growth temperature and growth sequence were optimized to grow high-quality InGaP layers with defect-free heterointerfaces. By PL measurements on <001>- and <311>-oriented samples simultaneously grown under the same growth conditions, existence of natural ordering in <001>-oriented samples was found. The so-called long-range order parameter, η, of the InGaP layer increased with increase of the TBP flow rate and with decrease of the growth rate. η could be changed in the range of 0.06–0.29 by changing the growth conditions, corresponding to the band gap change of 43 meV. The valence band offset (ΔEV) measured by in situ XPS method was 0.29 eV and was independent of the value of η. The change of conduction band offset (ΔEC) due to ordering caused a corresponding change in the sheet carrier density of two-dimensional electron gas at the heterointerface. No significant contribution from piezoelectric or spontaneous polarization was seen up to η=0.29.