Low-Pressure Chemical Vapor Deposition

In this chapter we review some of the major practical situations in which low pressure is used during the growth of semiconducting materials by chemical vapor deposition. Growth at subatmospheric pressure offers significant advantages for silicon grown from silane, and for the 111- V compounds InP, GaAs, GalnAs, and GalnAsP grown from organometallic sources by vapor phase epitaxy (OM-VPE). To understand the effect of pressure on growth it is necessary to have at least a qualitative knowledge of the physical and chemical processes involved in chemical vapor deposition (CVD). We therefore present a model of growth and of impurity incorporation that was initially developed for silicon growth but has since been applied, with some success, to the growth of compound semiconductors by OM- VPE. For each semiconduc­ tor we consider the practical growth system and then describe the material characteristics and applications in state-of-the-art devices.