Paper EM-ThM8
Mixed Anion ZnOTe Thin Films by Pulsed Laser Deposition

Thursday, October 18, 2007, 10:20 am, Room 612

deposition Zinc oxide and related wide-bandgap II-VI oxide alloys have received much interest for their potential application for optoelectronic and electronic devices. The primary challenges for this material remain the achievement of p-type material for junction devices, and alloy heterostructures to span the visible and ultraviolet spectral regions. The majority of recent research on ZnO and related alloys to address these challenges has focused on the doping of ZnO by group-V elements, and the investigation of mixed cation alloys CdZnO, MgZnO, and BeZnO. Very little attention has been given to mixed anion alloys related to ZnO. ZnTe is a II-VI compound semiconductor with a 2.29eV direct band gap, and typically exhibits p-type behavior. Furthermore, ZnTe has shown the ability for controllable p-type doping by nitrogen with hole concentrations of up to 1e20 cm-3. The ability to achieve p-type characteristics and the direct bandgap of ZnTe make mixed anion alloys based on ZnO and ZnTe attractive for optoelectronic devices including visible light emitters and solar cells. In this work, we report on mixed cation ZnOTe thin films deposited by pulsed laser deposition. Thin films were deposited on sapphire and GaAs substrates using a pulsed excimer laser, ZnTe target, and varying ambients oxygen, nitrogen, and high vacuum. Deposition under high vacuum resulted in crystalline ZnTe thin films with optical bandgap energy of approximately 2.3 eV based on transmission and reflectance measurements. Deposition under nitrogen ambient shows a significant red shift in optical bandgap energy, likely due to energy states introduced by nitrogen doping. Deposition of ZnTe under oxygen ambient results in a large blue shift in optical bandgap to more than 3.1 eV, with a strong dependence on oxygen partial pressure. The structural, electronic, and optical properties of these ZnOTe thin films will be presented.