Neutralization of Shallow-Donor Impurities

For depth inhomogeneities in the free electron concentration n x) and electron mobility the Hall-effect measurement yields an effective 

To eliminate the above uncertainties in the interpretation of the transport data, Hall-effect measurements were combined with layer removal on homogeneously doped n-type layers (Johnson and Herring, 1988a). The 

An example of the temperature dependence of donor neutralization is shown in Fig. 3. Devices with a square van der Pauw geometry were exposed to H° for 30 min. at different temperatures. Hydrogenation reduces the free-electron concentration over the entire investigated temperature range, with a maximum reduction of approximately 40% at 140°C. In 

HYDROGEN NEUTRALIZATION OF SHALLOW-DONOR IMPURITIES IN ARSENIC-DOPED EPILAYERS ON SILICON 

Dependence on hydrogenation temperature of the free-electron concentration (a) and the electron Hall mobility (b) in phosphorus-implanted n-type silicon (Johnson et al., 1987c). 

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In electrically neutral semiconductor samples, random internal electric fields can be present at low temperature because of the compensation and/or of the simultaneous presence of the electrically-charged deep centres. The following estimation of the effect of random internal electric fields on shallow impurity levels is taken from [123] who used it for a qualitative explanation of the broadening of some donor lines in NTD silicon [67], and from [64], who presented it in a more general form. 

The FEs can bind to neutral shallow impurities and become bound excitons (BEs), with a value of Eex slightly larger than the one of the FE. The difference is called the localization energy E oc of the BE. For the P donor, it is 4 meV in silicon, but 75 meV in diamond. E oc is given approximately by Haynes empirical rule [20] as 0.1 A, where A is the ionization energy of the impurity. BEs are created by laser illumination of a semiconductor sample at an energy larger than Eg and the study of their radiative recombination by PL... 

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