Structural, optical and electrical properties of SnN codoped p type ZnO thin films prepared by spray pyrolysis technique for diode applications

• N monodoping resulted in conductivity inversion, but highly resistive.
• SnN codoping resulted in highly textured p type ZnO thin film.
• Hole concentration enhanced and hence resistivity decreased with SnN codoping.
• Energy gap increased due to Burstein-Moss effect.
• Suitable for thin film optoelectronic applications including diodes.

The efficacy of tin-nitrogen codoping (SnN) in ZnO thin films deposited on glass substrates by spray pyrolysis technique to achieve a p type transparent conductive material is investigated. Monodoping ZnO with N altered the conductivity type but the resistivity is too high making it practically impossible to be useful in optoelectronic applications. But SnN codoping increased the hole concentration and obtained comparatively low resistivity because codoping enhanced the acceptor incorporation by forming acceptor-donor-acceptor complex in the band gap. The XRD analysis revealed the dependence of dopant incorporation on the texture and microstructure of the ZnO thin films. Further, the optical energy gap of N doped film decreased compared to undoped one due to the merging of impurity bands with the valence band while higher energy gap value for codoped film which might be due to the Burstein-Moss effect arising from increase in carrier concentration and also due to degraded crystallinity.