Effect of Annealing on the Dark and Illuminated I(V ) Characterization of a ZnO:Ga|Cu2O Hetero-Junction Prepared by Ultrasonic Spray System

Semiconductors - This paper presents the Ultrasonic Spray Pyrolysis system fabrication of gallium-doped zinc oxide (ZnO:Ga)|cuprous oxide (Cu2O) thin film hetero-junction. The deposition parameters...     

Extraction of the Defect Density of States in Microcrystalline Silicon from Experimental Results and Simulation Studies

The constant photocurrent method in the ac-mode (ac-CPM) is used to determine the defect density of states (DOS) in hydrogenated microcrystalline silicon (μc-Si:H) prepared by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD). The absorption coefficient spectrum (ac-α (hν)), is measured under ac-CPM conditions at 60 Hz. The measured ac-α (hν) is converted by the CPM spectroscopy into a DOS distribution covering a portion in the lower energy range of occupied states. We have found that the density of valence band-tail states falls exponentially towards the gap with a typical band-tail width of 63 meV. Independently, computer simulations of the ac-CPM are developed using a DOS model that is consistent with the measured ac-α (hν) in the present work and a previously measured transient photocurrent (TPC) for the same material. The DOS distribution model suggested by the measurements in the lower and in the upper part of the energy-gap, as well as by the numerical modelling in the middle part of the energy-gap, coincide reasonably well with the real DOS distribution in hydrogenated microcrystalline silicon because the computed ac-α (hν) is found to agree satisfactorily with the measured ac-α (hν).