An experimental determination of the carrier lifetime in p-i-n diodes from the stored carrier charge

In a p - i - n diode carrying forward current, the increase of carriers in the weakly-doped middle zone depends upon the carrier lifetime τ. For the same forward current ( I Du ), the increase of carriers is higher the larger τ. The stored charge Q S in the middle zone is, therefore, a direct measure of the lifetime at ‘high-injection’. For a known geometry, the lifetime τ and the related carrier concentration n are determinable from two measureable quantities; the current I Du and the charge Q S . Experimentally, the stored charge can be extracted by a suddenly applied blocking impulse, and quantitatively determined if the duration of this procedure is so short that the loss due to recombination is negligible. This requirement is fulfilled by a suitably large blocking current ( I R ⪢ I Du ). Measurements upon alloyed p - i - n silicon rectifiers yield the so-called ‘high-level’ lifetime for different excess concentrations n . The agreement with other values of τ = f ( n ) obtained from H erlet's characteristic curve analysis is very good.