When a material is irradiated,it becomes more electrically conductive due to the absorption of the electromagnetic radiation.As a result,the number of free electrons and holes changes and raises its electrical conductivity. A simple but interesting phenomenon to characterise a fabricated n~+p photodetector in order to determine its linearity(photoresponse) and photoconductance was employed.Using the transient decay when the irradiation source is switched off,the minority carrier concentration,effective lifetime and surface recombination velocity present at the surface of the detector were measured. When a material is irradiated, it becomes more electrically conductive due to the absorption of the electromagnetic radiation. As a result, the number of free electrons and holes changes and raises its electrical conductivity. A simple but interesting phenomenon to characterise a fabricated n ~ + p photodetector in order to determine its linearity (photoresponse) and photoconductance was employed. Using the transient decay when the irradiation source is switched off, the minority carrier concentration, effective lifetime and surface recombination velocity present at the surface of the detector were measured.