Measurement of electron lifetime, electron mobility and band-gap narrowing in heavily doped p-type silicon

The parameters that control the transport of minority carriers in heavily doped Si:B have been measured by a combination of steady state electrical and transient optical techniques. Electron diffusion length and electron lifetime measurements have been conducted on doped-as-grown wafers to extract the minority carrier electron mobility as a function of acceptor doping density. Effective band-gap narrowing in p
⁺
epitaxial layers has been characterized using bipolar test structures. Significant findings: 1) the electron mobility is about 2.5 times larger in heavily doped p-type Si than in n-type. 2) bandgap narrowing exceeds 120 meV at N
_{A} = 2 \times 10^{20}
cm
^-3
.3) minority electron lifetime in processed p
⁺
Si is not well modeled over a large doping range by an "Auger" coefficient.