Module 9 : Photo Detectors
Lecture : Principle of Photo Detection
 

Consider an n-type semiconductor. If the recombination life time for the minority carriers is $ \tau_p$, the rate of change of carrier concentration is given by

$\displaystyle \frac{d}{dt}(\Delta p) = \frac{\eta\alpha I}{h\nu}-\frac{\Delta p}{\tau_p}$

Under steady state condition $ d\delta p/dt=0$, which gives

$\displaystyle \delta p = \frac{\eta\alpha I_p\tau_p}{h\nu}= \Delta n$

This excess hole density leads to an additional conductivity

$\displaystyle \Delta\sigma = q\delta n\mu_e + q\Delta p \mu_h$
   
   
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