Interfacial Defects in SiO2Revealed by Photon Stimulated Tunneling of Electrons

Abstract

Experiments on the photon stimulated tunneling of electrons at the interfaces of SiO 2 with Si and SiC demonstrate the presence of defects with electron binding energy of 2.8 eV relative to the SiO 2 conduction band, well above the semiconductor band gap. These defects, which so far escaped direct detection, are located near interfacial oxide layers, their density being sensitive to the silicon enrichment of SiO 2 . The discovered defects appear to be the origin of the trap-assisted electron injection phenomena in SiO 2 . [S0031-9007(97)02708-7]

Effect of boron incorporation on slow interface traps in SiO2/4H-SiC structures

“…Parallel shifts in the C-V curves in the positive direction were observed for the dry and NO-annealed oxides that depended on the start voltage, suggesting that the electrons were captured in the traps located on the oxide side of the interface [14,15]. The electrons are thought to be captured by the NITs whose energy position is aligned close to the conduction band edge of 4H-SiC [11][12][13][14] because the Fermi level is very close to the conduction band edge in strong accumulation conditions. The time constant of the NITs is long because of the separation from the interface [11][12][13].…”

“…The electrons are thought to be captured by the NITs whose energy position is aligned close to the conduction band edge of 4H-SiC [11][12][13][14] because the Fermi level is very close to the conduction band edge in strong accumulation conditions. The time constant of the NITs is long because of the separation from the interface [11][12][13]. The electrons trapped in the NITs act like negative fixed charges in the oxide at 80 K, and, as a result, a parallel shift of the C-V curves in the positive direction was observed.…”

“…If the electrons are captured by the NITs, the channel electron density is reduced and the estimated field-effect mobility decreases. Although the NITs are believed to be located in the oxide within a few nanometers of the interface [11,13], some of them may also impede the channel electron transport due to remote Coulomb scattering.…”

“…Afanas'ev et al suggested that the NITs are inherent defects in SiO 2 located near the interface, and their energy position is 2.8 eV below the conduction band edge of SiO 2 [11,13]. Schöner et al also suggested that the defect levels close to the conduction band edge of SiC are identical for 4H-, 6H-, and 15R-SiC, and they are energetically pinned at around 2.9 eV above the valence band edge of all the SiC polytypes [28].…”

“…Afanas'ev et al suggested three possible origins for the interface states at the SiO 2 /4H-SiC interface: (i) Si or C dangling bonds, (ii) C clusters, and (iii) near-interface traps (NITs) [11,12]. Of these, NITs may play a dominant role because they are considered to create trap levels close to the conduction band edge of 4H-SiC at a high density [11][12][13][14]. It has been reported that NITs can be effectively removed by the incorporation of N [15], Na [16], K [17], and P [18] as revealed either by using low-temperature capacitance-voltage (C-V ) [15,18] or thermal dielectric relaxation current (TDRC) [16][17][18] measurements.…”