On the electrical properties of Si-doped InGaP layers grown by low pressure - metalorganic vapour phase epitaxy

The electrical properties of undoped and Silicon doped InGaP layers grown lattice matched on GaAs by low pressure Metal-Organic Vapour Phase Epitaxy were investigated under different growth conditions. The possible presence of superlattice ordering was excluded by photoluminescence analysis. Undoped layers exhibited a background p-type contamination of the order of 1016 cm-3; the role of possible Carbon contamination is discussed. Capacitance-Voltage and Hall investigation of Si-doped n-type layers evidenced a room temperature free electron density linearly increasing from 3.6×1016 to 6×1018 cm-3 as a function of the Si precursor flow. The corresponding electron mobilities decreased from 1800 to 483 cm2/Vs. At lower temperatures, the conductivity and mobility of the n-doped samples showed a metallic like behaviour, in some cases with values not consistent with a simple electronic transport into the conduction band, suggesting the presence of an additional parallel transport channel. Five main electron traps were identified by Deep Level Transient Spectroscopy and among them, two traps resulted dominant, one turned out to play a major role in the bulk, probably associated to the Si doping, and the other active near the InGaP surface, ascribable to P-related defects