ARS 202N Closed Cycle Refrigerator System (5.5-450K) or continuos flow liquid Nitrogen cryostat (100-475K)

HP 54510B Digitizing Oscilloscope (300MHz, 1GSa/s)

Home-made electronics to obtain 0.5micro seconds resolution.
Combined measurements of steady state photoconductivity and photoconductivity response time were used to obtain the drift mobility of majority carriers. There are two conditions to the method. The first requires single-carrier dominated photocurrent. In a-Si:H electrons are the dominant photocarrier. The second is the assumption that the recombination is described by a single time constant, the free carrier lifetime. Wherever the above-mentioned conditions hold, photoconductivity is given by,

The drift mobility of the electrons is then obtained in terms of experimentally measured quantities:


In the first two relations mu, e and G are respectively, the microscopic mobility, the electronic charge and the electron-hole generation rate. The quantum efficiency is assumed to be unity. The response time, tau(r), is determined from the initial slope of the photodecay curve: