Electrical and optical characteristics of molecular beam epitaxial Be-doped In0.53Ga0.26Al0.21As layers grown lattice-matched on InP (100) substrates

This paper reports the effects of beryllium (Be) doping in In_0.53Ga_0.26Al_0.2As layers grown lattice-matched to InP (100) substrates by molecular beam epitaxy (MBE). Hall effect measurements showed that hole concentrations as high as 2.94×10¹⁹ cm⁻³ was achieved, and the concentration decreased with further increase in the Be cell temperature. Depending on the hole concentration, good optical quality was achieved as verified by photoluminescence (PL) measurements. X-ray diffraction (XRD) measurements showed lattice mismatch values of lower than 8.6×10⁻⁴ in most samples. An intense PL peak (5 K) at 1.089 eV which is attributed to band-acceptor recombination was observed from the sample with the lowest hole concentration of 2.28×10¹⁶ cm⁻³. This sample exhibited the lowest PL full-width at half maximum (FWHM) of 8 meV (at 5 K) for the free exciton recombination. To the best of our knowledge, this is the lowest value reported to date. An increase in the hole concentration caused a merging of the band-acceptor and free excitor recombination lines to form a broad PL spectrum. A shift in the free exciton peak position in the PL spectrum was observed following an increase in the hole concentration, an effect which was probably due to degeneracy.