Band offsets of atomic layer deposited Al 2 O 3 and HfO 2 on Si measured by linear and nonlinear internal photoemission

We present measurements of band alignment of atomic layer deposited high‐ k dielectrics on Si(100) using linear internal photoemission (IPE), detected by measuring photocurrent from a biased MOS capacitor, and internal multi‐photon photoemission (IMPE), detected by optical second‐harmonic generation (SHG). In IPE, Band offsets are extracted from either the threshold of quantum yield; in IMPE, they are determined by detecting discrete increments in multi‐photon order. IPE and IMPE yielded identical conduction band (CB) offsets (2.0 eV) for as‐deposited Si/Al 2 O 3 structures with 10 and 3 nm oxides, respectively, in excellent agreement with previous measurements of annealed structures. Band offset measurements for Si/HfO 2 , on the other hand, show a strong (0.3 eV) upshift of the oxide valence band (VB) maximum, and an equal decrease of the oxide band gap upon post‐deposition annealing (PDA) at 600 °C, while the CB offset remains unchanged. We attribute the shift of the VB edge to thermally driven oxygen diffusion away from the Si/HfO 2 interface.