Surface and electrical properties of plasma processed RF sputtered GaN thin films

Nano Optoelectronics Research Laboratory, School of Physics, Universiti Sains Malaysia (USM), 11800 Minden, Pulau Pinang, Malaysia

^a e-mail: subashanmugan@gmail.com

Received: 25 May 2014
Revised: 19 August 2014
Accepted: 20 August 2014
Published online: 5 December 2014

Abstract

Plasma processing is an approach to modify the surface structure for improved performance of nitride semiconductor using in light emitting diodes. In this work, RF sputtered GaN thin films were synthesized on Si (1 0 0) substrates and processed at two different plasmas (N₂ and O₂) at various flow rates. The surface nature of plasma processed thin films was characterized using atomic force microscope (AFM) and scanning electron microscope (SEM). Energy dispersive spectrum (EDS) of all samples was recorded to do elemental analysis. Noticeable changes on surface morphology were recorded for the plasma processed GaN thin films at high flow rate (>20 sccm). The roughness and particle size of thin film got decreased as the flow rate of gases increased. Low value in surface roughness (0.26 nm) and particles size (14 nm) was observed at 30 sccm flow rate of O₂. SEM images also revealed the surface modification at high gas flow rates during plasma process. Nitrogen deficient GaN thin film was confirmed by EDS spectra and improved N₂ concentration was achieved for N₂ and O₂ plasma processing upto 20 sccm flow rates. I-V characteristics showed the Schottky-contact behavior for all thin films and revealed the improved surface quality to make good ohmic contact for the film processed at high gas flow rate (>30 sccm).