Optimisation of PLD Parameters

Progress in the fabrication of ZnO-based optoelectronic devices lies in producing reproducible, reliable and stable p-type ZnO films, because of the intrinsic n-type nature of the deposited ZnO films. Hence, for successful conversion of its carriers from n-type to p-type, it is desirable that the deposited ZnO film has as low an electron concentration as possible. Moreover, for the fabrication of optoelectronic devices, the films should have very high optical quality. The growth of highly oriented films with the least strain will offer an added advantage in fabricating these devices. Hence, the deposition parameters of temperature and pressure using pulsed laser deposition (PLD) were optimised keeping these things in mind. A substrate temperature of 650 °C and oxygen pressure of 40 mTorr were found to be optimised growth parameters as it had the lowest carrier concentration of 1.01 × 1017 cm−3 a reasonably high Hall mobility of 16.1 cm2 V−1 s−1 and also had the highest optical quality. Once the PLD parameters were optimised, hydrogen implantation was carried out to see whether it further enhanced the electrical and optical properties of the thin film. While the Van der Pauw Hall measurements did not reveal any significant changes in the electrical characteristics of the thin films, the optical quality of the implanted films was found to increase by two orders of magnitude when compared to the as-deposited sample. Such an enhancement in the optical luminescence of the ZnO thin films may be helpful in fabricating highly efficient ZnO-based devices.