SURFACE FERMI LEVEL ENGINEERING - OR THERES MORE TO SCHOTTKY BARRIERS THAN JUST MAKING DIODES AND FIELD-EFFECT TRANSISTOR GATES

Surface scientists argue about the fundamental nature of Schottky barriers, or more precisely what determines the location of the Fermi level at semiconductor surfaces and interfaces. Electrical and materials engineers worry about how to make Schottky barrier diodes and gates to field effect transistors and the control of barrier heights. There is some interesting middle ground in which the location of the surface and interface Fermi level can, for example, determine semiconductor doping characteristics during crystal growth. In keeping with the trendy fashion of the 80's to invent "catchy phrases" to describe marginally important new fields, we dub this middle ground as "surface Fermi level engineering." Within the framework of this concept, we will discuss several interesting and well known examples of doping characteristics which are still somewhat mysterious. Specifically, we will address the following questions: (1) why is Ge doped GaAs p type when grown from Ga melts but n type when grown from Au melts? (2) why is low resistivity p type ZnSe, AlAs, and AlGaInP hard to make, and more importantly, how can we fix this problem? In addition we will describe how this concept relates to the electronic properties of a new type of GaAs, GaAs:As, which contains a high density of As precipitates.