Estimation of Device Parameters and C-V Modeling of Pulsed Laser Deposited Phosphorus Doped Carbon/p-Silicon Heterostructure

A heterostructure, fabricated by depositing phosphorus (P) doped carbon thin film, thickness of which is about 200 nm, on boron doped crystalline silicon (Si) substrate by pulsed laser deposition (PLD) technique, is studied in terms of its opto-electronic characteristics. Optical transmittance-reflectance measurements, temperature dependent conductivity data and the current density-voltage (J-V) characteristics of the heterostructure are analyzed to estimate device parameters, such as built-in potential, reverse saturation current density, intrinsic carrier concentration and donor concentration in the carbon side of the device for different P content in the target material for carbon. The estimated device parameters are seen to improve with the increase in P content in the target for up to 5% of P. But for 7% of P in the target, the device performance deteriorates. Using these device parameters, capacitance-voltage (C-V) characteristics of the device is simulated. The results are then compared with the experimentally obtained C-V characteristics. The detailed analyses suggests diffusion of P atoms from the film into the Si region during the film deposition by pulsed laser ablation and thus the formation of a P-I-N device rather than a simple P-N junction device. The width of the I region and diffusion co-efficient of P into the Si are estimated and the values are found to be in the acceptable range.