Electron Band Alignment at Interfaces of Semiconductors with Insulating Oxides: An Internal Photoemission Study
(a) Semilogarithmic plot of the IPE quantum yield as a function of photon energy measured on n-type (P-doped, cm−3) (100)Si/HfO2 (17 nm)/Au sample with the applied bias varying from 1 V to 4 V. The inset illustrates the schematic of the IPE type electron transitions (A) and the transitions associated with photoionization of near-interface oxide traps (“pseudo-IPE”, B). The arrows and indicate onsets of direct optical transition in the silicon crystal. (b) Cube root of the IPE yield as a function of photon energy as inferred from the data shown in the panel (a) after subtracting the “pseudo-IPE” background photocurrent. The inferred spectral threshold of electron IPE from the VB of Si into the CB of HfO2 is indicated by the vertical arrow.