Reactor Design for a-Si

The aim of this chapter is to analyze the reactor design for a-Si: H deposition in terms of electrical power dissipation, electron acceleration mechanisms, and discharge regimes. It examines the material balance and SiH4 conversion efficiency into a-Si: H and the main ingredients of the gas-phase and surface physicochemistry controlling the film growth and the final a-Si: H properties. This chapter discusses the electrical power dissipation in the discharge, and emphasizes the different mechanisms by which energy is coupled to the electrons and released into dissociation, ionization, attachment, and vibrational excitation of the molecules and eventually ends up on the walls via exothermic chemical reactions, gas heating, and thermal diffusion. It presents the material balance in terms of gas flow and SiH4 dissociation efficiency and the basic effects of gas phase and surface physicochemistry on the a-Si: H film quality in relation to the external reactor control parameters. This chapter also reviews the various types of reactors and their respective advantages and limitations. It also discusses alternative a-Si: H deposition methods and reactive sputtering.