Dopant dependent

The Hall effect provides a measure of the net carrier concentration of the dopants. Depending on the depth of the dopants, the activation of the impurity can be very much reduced. For example, Mg in GaN forms a level at 250 meV above the valence band, and the percentage of activation of the magnesium atoms at room temperature is about 1%. DLTS provides a measure of the deep states within the bandgap of the semiconductor. However, it only provides the activation energy and the impurity concentration, and it does not give the exact nature of the impurity concerned. Implantation experiments are required to correlate known impurities with the energy levels measured by DLTS. 

A different application of chemical equilibrium leads to an explanation of how the incorporation of defects and dopants depends on the growth conditions (Winer and Street 1989). Section S.l describes the unexpected rf power and gas concentration dependence of the dopant distribution coefficient, particularly for arsenic doping. A schematic diagram of the growth process is shown in Fig. 6.19, in which three-fold and four-fold silicon and dopants are deposited from the gas phase. The deposition reactions proposed for arsenic doping are... 

Several chemical etchants can etch silicon isotropically or anisotropically, be dopant-dependent or not, and have a wide range of selectivity to silicon, which determines the appropriate masking material. Brief but clear descriptions of the silicon chemical etchants and their properties can be found in [2-4, 7]. 

Aqueous alkaline etchants, such as TMAH [10], KOH [7], NaOH [11], and CsOH [12], all etch silicon anisotropically with good selectivity to silicon nitride or oxide. They are all dopant dependent, etching silicon layers highly doped with boron slowly or not at all. 

Dopant dependence on bath age necessitated the preparation of baths with controlled age. In order to accomplish this, bath samples were obtained from IBM s semiconductor development site at East Fishkill, New York, and mixed with fresh baths with the same composition. Typically aged baths had been in operation in excess of 1 year. Mixing ratios of 25 % by volume fresh bath + 75 % by volume aged bath, 50/50, and 75/25 were used together with 100 % fresh and 100 % aged baths. Bath age was measured by HPLC [6]. 

Druy et al. [29] reported that the kinetic studies on d.c. electrical conductivity decay of p-type doped Shirakawa polyacetylene in an inert atmosphere and indicated that two types, namley dopant dependent and dopant independent reactions, are involved in the degradation process of polyacetylene. It was observed... 

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