Abstract
The optical absorption coefficient in ultrathin (∼10 Å) hydrogenated amorphous germanium (a‐Ge:H) layers deposited on hydrogenated amorphous silicon layers was determined by in situ reflectivity measurements. The decrease in the absorption coefficient in the ultrathin a‐Ge:H layers, compared to that of thick films, is explained by an upward shift in the conduction band edge due to quantum confinement of electrons with effective mass of 0.4m0.