Study of conductivity type of undoped ZnO films grown on n and p-type (100) Si substrates by pulsed laser deposition

A study of the conductivity type of undoped high quality ZnO thin-films grown on (100) Si substrates by pulsed laser deposition (PLD), is reported. Two groups of samples were prepared at a wide range of growth temperatures between 150 and 350°C and oxygen overpressure of 5.5×10^-6 Torr (low oxygen pressure regime) for one group and 2.5×10^-4 Torr (high oxygen pressure regime) for the other group. The electrical properties of the samples were studied by Hall Effect measurements using the four-point van der Pauw method. The measurements were performed using an Ecopia HMS-5000 Hall Effect Measurement System, with fixed magneto-flux density of 0.51T, and injected current that can be controlled between 1nA to 20mA. The system allows for variable temperature readings between 77 and 350K. Standard photolithography was used to prepare a cloverleaf mesa pattern of ZnO for the Hall Effect measurements.