Measurement of Electron Mobility in p-Si by Time-of-Flight Technique

The time-of-flight technique was studied as a method of measuring the the minority-carrier mobility in p-type Si. The ambipolar diffusion equations were solved numerically, and it was found that the transit time is given by the time from the initial rise to the shoulder at the fall of the induced current waveform rather than the half-height width, even if the ambipolar effects are strong. For example, the transit time defined by the former agreed with the true transit time within an error of 2%, while the latter gave an error of up to 10%. To demonstrate the usefulness of the method, the drift mobility of electrons in p-type silicon was studied and the results were compared with those for majority ones.