The Influence of Interfaces on the Gap State Distribution of Undoped a-Si:H

1990 ◽  
Vol 192 ◽  
Author(s):  
G. Schumm ◽  
G. H. Bauer
Keyword(s):  
Fermi Level ◽  
Transit Time ◽  
Reverse Bias ◽  
State Distribution ◽  
Band Bending ◽  
Time Regime ◽  
Level Shifts ◽  
Pool Model ◽  
Annealing Effects ◽  
Gap State

ABSTRACTModulated primary photocurrent (MPC) studies on pin structures show spatial variations of the gap state distribution across the i-layer that can be correlated with Fermi level shifts by band bending towards interfaces. These results as well as reverse bias annealing effects are explained in terms of the defect pool model. It is demonstrated that MPC measurements are basically identical to TOF measurements with clear advantages in the post-transit time regime.

Photoelectron spectroscopic investigations of very thin a-Si:H layers

2003 ◽  
Vol 762 ◽  
Author(s):  
M. Schmidt ◽  
A. Schoepke ◽  
O. Milch ◽  
Th. Lussky ◽  
W. Fuhs
Keyword(s):  
Fermi Level ◽  
Gas Phase ◽  
Photoelectron Spectroscopy ◽  
Doping Level ◽  
Urbach Energy ◽  
Deposition Process ◽  
State Density ◽  
State Distribution ◽  
20 Nm ◽  
Gap State

AbstractWe report on a detailed study on gap-state distribution in thin amorphous silicon layers (a-Si:H) with film thicknesses between 5 nm and 20 nm on c-Si wafers performed by UV excited photoelectron spectroscopy (UV-PES). We measured how the work function, the gap state density, the position of the Fermi-level and the Urbach-energy depend on the layer thickness and the doping level of the ultra thin a-Si:H(n) layers. It was found, that for phosphorous doping the position of the Fermi level saturates at EF–EV=1.47 eV. This is achieved at a gas phase concentration of 10000 ppm PH3 in the SiH4/H2 mixture which was used for the PECVD deposition process. The variation of the doping level from 0 to 20000 ppm PH3 addition results in an increase of the Urbach energy from 65 meV to 101 meV and in an increase of the gap state density at midgap (EV-Ei= 0.86eV) from 3·1018 to 2·1019 cm-3eV-1.

Fermi level pinning and band bending in δ-doped BaSnO3

2021 ◽  
Vol 118 (5) ◽  
pp. 052101
Author(s):  
Youjung Kim ◽  
Hyeongmin Cho ◽  
Kookrin Char
Keyword(s):  
Fermi Level ◽  
Band Bending ◽  
Fermi Level Pinning

Gap state distribution and Fermi level pinning in monolayer to multilayer MoS2 field effect transistors

Nanoscale ◽  
2020 ◽  
Vol 12 (16) ◽  
pp. 8883-8889 ◽  
Author(s):  
Ronen Dagan ◽  
Yonatan Vaknin ◽  
Yossi Rosenwaks
Keyword(s):  
Transition Metal ◽  
Fermi Level ◽  
Field Effect ◽  
Field Effect Transistors ◽  
High Surface ◽  
Volume Ratio ◽  
Transition Metal Dichalcogenide ◽  
State Distribution ◽  
Fermi Level Pinning ◽  
Gap States

Gap states and Fermi level pinning play an important role in all semiconductor devices, but even more in transition metal dichalcogenide-based devices due to their high surface to volume ratio and the absence of intralayer dangling bonds.

SHG(Second Harmonic Generation) in Reflection from GaAs Surfaces during Sulfur Passivation and Photochemical Washing Processes

1992 ◽  
Vol 259 ◽  
Author(s):  
Chikashi Yamada ◽  
Takahiro Kimura ◽  
Peter Fuqua
Keyword(s):  
Second Harmonic Generation ◽  
Fermi Level ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Band Bending ◽  
Remarkable Similarity ◽  
Fermi Level Pinning ◽  
Sulfur Passivation ◽  
Intensity Changes ◽  
Pl Intensity

ABSTRACTA passivation processes using Na2S and photochemical washing of GaAs (100) surfaces was studied in real time by a second-harmonic generation (SHG) technique. The intensities of surface-specific SHG signals were compared with those of photoluminescence (PL) signals. We found a remarkable similarity between the SHG and PL intensity changes during these processes. A band-bending model due to Fermi-level pinning at the surface has been applied in order to account for both the SHG and the PL intensity changes.

Defect states in amorphous Ge2Sb2Te5 phase change material

2014 ◽  
Vol 92 (7/8) ◽  
pp. 619-622
Author(s):  
N. Qamhieh ◽  
S.T. Mahmoud ◽  
A.I. Ayesh
Keyword(s):  
Fermi Level ◽  
Energy Gap ◽  
Continuous Distribution ◽  
Dark Conductivity ◽  
Localized States ◽  
Defect States ◽  
Thermally Activated ◽  
Level Shifts ◽  
Gap States ◽  
Change Material

Steady-state photoconductivity measurements in the temperature range 100–300 K on amorphous Ge2Sb2Te5 thin film prepared by dc sputtering are analyzed. The dark conductivity is thermally activated with a single activation energy that allocates the position of the Fermi level approximately in the middle of the energy gap relative to the valance band edge. The temperature dependence of the photoconductivity ensures the presence of a maximum normally observed in chalcogenides with low- and high-temperature slopes, which predict the location of discrete sets of localized states (recombination levels) in the gap. The presence of these defect states close to the valence and conduction band edges leaves the quasi Fermi level shifts in a continuous distribution of gap states at high temperatures, as evidenced from the γ values of the lux–ampere characteristics.

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