Determination of insulator bulk trapped charge densities and centroids from photocurrent-voltage charactersitcs of MOS structures

A new rapid technique for determining the density and centroid of trapped space charge in MOS structures is described. Photocurrent-voltage characteristics for both the metal-oxide and Si-oxide interfaces are used to determine the internal fields due to bulk trapped charge and, hence, its density and centroid. An experimental example of this technique is shown for a MOWOS (metal-SiO2-W-SiO2-Si) structure where a layer of approximately 1014 W atoms/cm2 deposited 80 or 42 Å from the Si-SiO2 interface and charged by internal photoemission is investigated. This technique is compared to others in terms of its direct, rapid, minimally perturbing, low-current and low-field characteristics.