Future Trends in Microelectronics: Up the Nano Creek

A New Class of Semiconductors Using Quantum Confinement of Silicon in a Dielectric Matrix

Martin A. Green

ARC Photovoltaics Centre of ExcellenceUniversity of New South Wales, Sydney 2052, Australia

1.   Introduction

For photovoltaic use, control of the semiconductor bandgap is important for high energy conversion efficiency designs, such as those based on tandem stacks of cells responding to different spectral ranges. Traditionally, such bandgap control has been obtained using alloys of III-V semiconductors or by Si/Ge alloys in the case of amorphous material. This chapter explores the use of quantum confinement to produce high bandgap material within the crystalline silicon materials system. The optical and transport properties of a new form of synthesized material involving silicon quantum dots in a dielectric matrix of silicon oxide, nitride or carbide are described. These materials may have applications in areas other than photovoltaics where low mobility is tolerable.

The photovoltaics industry is currently booming, with annual sales growing at over 40%/year. This growth is expected to continue into the next decade.¹ Most solar sells are based on silicon wafers similar to those used in microelectronics. In 2006, a turning point was reached where the volume of silicon used in photovoltaics exceeded that used in microelectronics for the first time. Traditional polysilicon suppliers are now rapidly increasing capacity to meet the rapidly increasing demand.¹ With over 2 gigawatts ...