Relationship between passivation properties and band alignment in O₃-based atomic-layer-deposited AlO_xon crystalline Si for photovoltaic applications

Abstract

The passivation properties and band structures in aluminum oxide (AlOx) deposited by ozone-based atomic layer deposition (ALD) at room temperature on p-type crystalline silicon were investigated by X-ray photoelectron spectroscopy (XPS). The effective carrier lifetime depends on the thickness of AlOx films, since the field effects induced in the films by fixed charges depend on film thickness. The fixed charges are different by two orders of magnitude between films with thicknesses of 10 and 30 nm. At the 30-nm-thick AlOx/Si interface, the completely accumulated band bending of the Si surface was observed. On the other hand, a thin depletion layer was formed at the 10-nm-thick AlOx/Si interface. From the time-dependent XPS measurements, a hole trap was observed toward AlOx, in which trapping centers existed.

Effect of post-deposition annealing on electrical properties and structures of aluminum oxide passivation film on a crystalline silicon substrate

“…Although AlO x has been studied as a candidate for gate dielectric since the 1970s, research on AlO x for passivation films has been active since the mid-2000s, because the AlO x film on c-Si showed excellent surface passivation property. This high level of surface passivation is attributed to the field-effect passivation induced by a high negative fixed charge density, regardless of the deposition techniques, such as atomic layer deposition (ALD), [8][9][10][11][12][13][14][15][16][17] plasma-enhanced CVD, [18][19][20] mist CVD, 21) pyrolysis 7) and sputtering. 22,23) In most cases, post-deposition annealing (PDA), so called "activation" was carried out to obtain such excellent surface passivation property.…”

Evaluation of band offset at amorphous-Si/BaSi2 interfaces by hard x-ray photoelectron spectroscopy

“…HAXPES is a fairly powerful method to analyze the VB density of states (DOS) of buried layers because of the large analysis depth. [27][28][29][30][31][32][33][34][35] Conventional x-ray photoelectron spectroscopy with the electron kinetic energy of 50-100 eV is quite surface sensitive due to the short electron inelastic mean free path (IMFP), k, of <5 Å . 36 It is thus difficult to analyze the electronic states inside solids.…”

“…[37][38][39] There have been several reports utilizing this large probing depth to measure VB spectra of buried layers such as native-oxide/BaSi 2 , CdS/Cu 2 ZnSnS 4 (CZTS), AlO x /Si heterostructures, and Bi 2 Se 3 surface. 24,[33][34][35] In Ref. 33, for example, Tajima et al have reported that the VBO at the CdS/CZTS interface was 0.0 6 0.1 eV.…”

Measurement of valence-band offset at native oxide/BaSi2 interfaces by hard x-ray photoelectron spectroscopy

“…This is because the analysis-depth of HAXPES is much deeper than that of conventional XPS and ultraviolet photoelectron spectroscopy. [20][21][22][23][24][25][26][27][28][29] In general, conventional XPS in the electron kinetic-energy range of 50-100 eV is quite surface sensitive due to the short electron inelastic mean free path (IMFP), k, of <5 Å . The conventional XPS spectra strongly reflect electronic states at surfaces of solids, 0021-8979/2016/119(2)/025306/5/$30.00 V C 2016 AIP Publishing LLC 119, 025306-1 which make it difficult to examine the electronic states inside the solids.…”

“…32 There have been several reports utilizing this large probing depth on the measurement of VB spectra of buried layers such as CdS/Cu 2 ZnSnS 4 (CZTS), AlO x /Si heterostructures, and Bi 2 Se 3 surface. [20][21][22] For example, in Ref. 20, CdS/CZTS heterostructures formed on Mocoated glass, where the CdS layer thickness was varied as 0, 5, and 100 nm, were examined by changing the effective IMFP, which was controlled by take-off angle (TOA) of photoelectrons in HAXPES.…”