Microstructural and electrical properties of MgO thin films grown on p-InP (100) substrates at low temperature

The growth of MgO thin films on p-InP (100) substrates by using electron-beam deposition at a relatively low temperature (∼200°C) was performed in order to produce high-quality MgO/p-InP (100) heterointerface and MgO insulator gates with dielectric constants of low magnitude. Atomic force microscopy and X-ray diffraction measurements showed that the MgO films grown on the InP substrates were polycrystalline thin layers with very smooth surfaces. Transmission electron microscopy and selected-area diffraction measurements showed that the grown MgO films were polycrystals with small domains and that the MgO/InP (100) heterointerface had no significant interdiffusion problem. Room-temperature current–voltage and capacitance–voltage (C–V) measurements clearly revealed a metal–insulator–semiconductor behavior for the diodes with MgO insulator gates, and the interface state densities at the MgO/p-InP interfaces, as determined from the C–V measurements, were approximately 4.5×1011 eV−1 cm−2 at an energy of about 0.7 eV below the conduction-band edge. The dielectric constant of the MgO thin films, as determined from the C–V measurements, was as low as 9.67. These results indicate that the MgO layers grown on p-InP (100) substrates at low temperature hold promise for potential electronic devices based on InP substrates.