Question

4. Photoconductivity ete. A. A sample of unknown semiconductor is subjected to light from a laser at 100 mW/cm2. The laser wavelength is 530 nm. The dimensions of the sample are given below in the diagram. α -I E4/cm. Reflection coeff. is 10%. T.-Tp I E-6 s. μη S000 cm'/V-s, and μ,-400 cm'/V-s Calculate i)incident photon flux ii)Absorbed photon flux iii)G, generation rate ivan and Δp due to light) v)Photo-conductivity vi)Photo Current when 10 V is applied to the sample. lem Lig B.Using the E-k diagram below, calculate the thermal and optical bandgaps 2.5 1.5 0.5

Answer 1

The given data is light from laser = 100 mw/cm^2 wave lengths = 530 mm alpha = Vertical-bar EU Vertical-bar cm Reflection coeff = 10%, T_0 = T_p = 1E - 6s H_0 = 5000 cm^2/v - s, H_p = 400 cm^2/v - s The light transmitted through the sample is given by I = I_0 (1 - r) = 0.9 times 100 = 90 mw/cm^2 The incident photon flux is given by phi = IA = 90 mw/cm^2 times 1 cm^2 = 90 mw In terms of photon number, we get phi = Nhc/lambda Rightarrow N = phi lambda/bc = 0.90 times 530 times 10^- 9/6.625 times 10^- 34 times 3 times 10^8 N = 2.4 times 10^17