Defect states in semiconductors, which act as charge trapping or recombination centres, often paramagnetic in nature or can be made paramagnetic by adjusting experimental conditions. Therefore, Electron Paramagnetic Resonance (EPR) is a powerful technique to investigate microscopic and electronic properties of these defect states. Conventional EPR can give information about environment of paramagnetic point defects, but it fails to give information about transport defects. Although conventional EPR is a powerful technique with typical sensitivity of the order of 10^10-11 paramagnetic defects at 9 GHz, it has some limitations such as saturation of signal intensity. Moreover, it is often impossible to discriminate the background substrate signals from actual signals of films. So, powder samples are measured in conventional EPR to avoid this problem. But, it is questionable to correlate defects from powder to thin films as boundaries have finite effect in film growth conditions. Due to this limitation a new method has been developed that combine the sensitivity of conventional EPR with conductivity, called Electrically Detected Magnetic Resonance (EDMR). Electrical detected EPR is a powerful tool to identify spin dependent processes (Spin dependent recombination, Spin dependent hopping, Bipolaron formation) in semiconducting devices directly as it is related to the measurement of conductivity change.