Diluted II-VI oxide semiconductors with multiple band gaps

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Physics

Background:

• Tuning semiconductor band gaps is crucial for advanced electronic and photovoltaic applications.
• Developing materials with multiple band gaps can enhance solar energy conversion efficiency.

Purpose of the Study:

• To synthesize and characterize a new mult-band-gap semiconductor, Zn(1-y)Mn(y)OxTe1-x.
• To investigate the effect of oxygen incorporation on the electronic band structure of Zn(1-y)Mn(y)Te.
• To evaluate the potential of the new material for single-junction photovoltaics.

Main Methods:

• Synthesis of Zn(1-y)Mn(y)OxTe1-x alloys via oxygen ion implantation and pulsed laser melting.
• Analysis of the band structure modification due to isovalent oxygen incorporation.
• Characterization of the resulting band gaps and interband transitions.

Main Results:

• Successful synthesis of Zn(1-y)Mn(y)OxTe1-x alloys with tunable band gaps.
• Observation of a narrow, oxygen-derived band of extended states within the host band gap.
• Formation of two direct band gaps at approximately 1.77 and 2.7 eV in Zn0.88Mn0.12OxTe0.87.
• Band structure modification explained by the band anticrossing model.

Conclusions:

• Zn(1-y)Mn(y)OxTe1-x is a novel mult-band-gap semiconductor with significant potential for photovoltaics.
• The material's multiple band gaps align with the solar spectrum, enabling high single-junction solar cell efficiencies.
• Theoretical power conversion efficiencies for single-junction devices could exceed 50%.