ELECTRONIC AND OPTICAL CHARACTERIZATION OF INGAP GROWN BY GAS-SOURCE MOLECULAR-BEAM EPITAXY

We have prepared films of InGaP on GaAs substrates using gas-source molecular-beam epitaxy. Unintentionally doped InGaP is n-type, with the net electron concentration as low as 1 X 10(15) cm-3 with associated 300 K mobility of 2100 cm2/V s. Photoluminescence and photoluminescence excitation spectra at 2 K of undoped InGaP films show free exciton luminescence with line widths as narrow as 8.5 meV. Such high quality InGaP layers were incorporated as the insulating layer into p(-)-i-p+ and n(-)-i-n+ GaAs-InGaP-GaAs heterojunction capacitors. Current-voltage characteristics of these structures indicate thermionic-emission barrier heights for holes of between 420 and 450 meV, indicating that the valence band discontinuity between GaAs and InGaP is very large, comprising up to 90% of the total band gap difference.