Interface-structure analysis of amorphous semiconductor heterojunctions by in situ x-ray photoelectron spectroscopy

The heterojunction interface of an amorphous semiconductor bilayer composed of hydrogenated amorphous silicon (a-Si:H) and hydrogenated and fluorinated amorphous silicon carbide (a-SiC:H,F) was analyzed with an atomic-scale resolution with use of in situ x-ray photoelectron spectroscopy. The intensity of photoelectron emission originating from carbon and fluorine in the a-SiC:H,F and transmitting through an a-Si:H overlayer was measured as a function of the a-Si:H layer thickness. The bilayers were fabricated by two different methods: a batch (i.e., gas-exchange) method and a continuous (i.e., excitation-energy- exchange) method. The interface fabricated by the batch process is ideally sharp, whereas that fabricated by the continuous method has a compositional transition region about 0.5 nm thick. Details of the deposition process are examined in order to explain this discrepancy.