Minority carriers contribution and hot-electron injection process in tunnel spectroscopy of H-passivated silicon surfaces

Tunneling spectroscopy on semiconductors with a low surface state density

“…However, on semiconductors with a low surface state density, such as H-terminated Si, cleaved GaAs͑110͒ or the layered materials WSe 2 and WS 2 , the situation is far more complex, since the applied tunneling voltage and the work function difference between the tip and the sample lead to an additional bandbending at the semiconductor surface and nonequilibrium effects need to be considered. [5][6][7][8][9][10][11][12][13][14] In a one-dimensional model the bandbending in a metalinsulator-semiconductor ͑MIS͒ diode was first determined by Garret and Brattain 15 and Kingston and Neustadter 16 by integrating the Poisson equation, including accumulation, depletion and inversion at the semiconductor surface. For a known bandbending the tunneling current can then be calculated using a tunneling theory for a MIS diode.…”

“…[5][6][7][8][9][10]14,17 The question whether this quasi-equilibrium approach is valid for STS measurements is still controversly discussed. 5,10,[12][13][14] It was first recognized by Feenstra and Stroscio 5 that due to an extraction of the minority charge carriers, the semiconductor surface might not invert for the reverse bias situation. Bolotov et al 13 were able to measure this minority charge carrier extraction current on H-terminated Si͑111͒ samples.…”

“…5,10,[12][13][14] It was first recognized by Feenstra and Stroscio 5 that due to an extraction of the minority charge carriers, the semiconductor surface might not invert for the reverse bias situation. Bolotov et al 13 were able to measure this minority charge carrier extraction current on H-terminated Si͑111͒ samples. Depending on the temperature and the level of doping, they observed a different saturation level in the tunneling current for the reverse bias situation.…”

“…[11][12][13][18][19][20][21][22][23][24] Using light with a photon energy of h ϾE g , electron-hole pairs are created in the semiconductor. On semiconductors with a high surface state density it is essentially the balance between photoexcitation, diffusion and surface recombination of the minority charge carriers, which leads to a lateral shift of the I -V curves under illumination, usually described by an additional local surface photovoltage ͑LSPV͒.…”

“…They showed that on H-terminated Si͑111͒ the presence of the tunneling tip and the applied tip-sample bias significantly influences the bandbending at the semiconductor surface. However, the contribution of direct tunneling of photoexcited carriers, as observed by several other authors, 12,13,[22][23][24] was neglected in their electrostatic approach to calculate the LSPV. On the other hand, an interpretation of the observed I -V curves under illumination by a simple superposition of dark current and voltage independent photocurrent, 12,23 as generally used for the description of macroscopic solar cells, cannot explain the experimental results.…”