Electrical Characterization of Organic Electronic Materials and Devices

Contents......Page 4
Preface......Page 12
1.2 Conduction mechanism......Page 16
1.3 Chemistry and the energy diagram......Page 21
1.3.1 Energy diagram of crystalline materials......Page 25
1.3.2 Energy diagram of amorphous materials......Page 32
1.4 Disordered materials and the Meyer–Neldel Rule......Page 39
1.5 Devices......Page 42
1.5.1 Resistor......Page 43
1.5.2 Schottky diode......Page 44
1.5.3 MIS diode and MIS tunnel diode......Page 46
1.6 Optoelectronics/photovoltaics......Page 50
2.1 Conductance......Page 53
2.1.1 Ohmic conduction......Page 60
2.1.3 Tunneling......Page 63
2.1.4 Space-charge-limited current......Page 67
2.1.5 Granular materials; grain boundaries......Page 68
2.2 DC current of a Schottky barrier......Page 72
2.2.1 High-current regime......Page 73
2.3.1 van der Pauw......Page 75
2.3.2 Hall effect......Page 77
3 Two-terminal devices: Admittance spectroscopy......Page 79
3.1.1 Low-frequency RCL bridge......Page 80
3.1.2 DC admittance......Page 86
3.2 Geometrical capacitance......Page 88
3.4 Resistor; SCLC......Page 89
3.5 Schottky diodes......Page 94
3.5.1 Schottky diode; nonuniform doping......Page 95
3.5.3 Schottky diode; minority levels......Page 99
3.5.4 Schottky barrier; temperature dependence......Page 103
3.6 MIS diodes......Page 105
3.6.1 MIS of doped semiconductors......Page 106
3.6.2 MIS with interface states......Page 107
3.6.3 MIS of low-mobility semiconductors......Page 114
3.7 MIS tunnel diode......Page 123
3.8 Noise measurements......Page 130
4 Two-terminal devices: Transient techniques......Page 132
4.1 Kinetics: Emission and capture of carriers......Page 134
4.1.1 Emission and capture in organic materials......Page 135
4.2 Current transient spectroscopy......Page 140
4.2.2 Example of a capture experiment......Page 141
4.3 Thermally stimulated current......Page 145
4.4 Capacitance transient spectroscopy......Page 148
4.4.1 Case study: Example of a capacitance transient measurement......Page 153
4.5 Deep-level transient spectroscopy......Page 160
4.6 Q-DLTS......Page 163
5 Time-of-flight......Page 166
5.2 Drift transient......Page 168
5.3 Diffusive transient......Page 170
5.4 Violating Einstein’s Relation......Page 177
5.5 Multi-trap-and-release......Page 183
5.6 Anomalous transients......Page 184
5.7 High current (space charge) transients......Page 189
5.8 Summary of the ToF technique......Page 195
6.1 Field-effect transistors......Page 199
6.2 MOS-FET......Page 204
6.2.1 MOS-FET threshold voltage......Page 206
6.2.2 MOS-FET current......Page 209
6.2.4 MOS-FET subthreshold current and subthreshold swing......Page 211
6.3 Introducing TFTs......Page 214
6.4 Basic model......Page 215
6.4.1 Threshold voltage and subthreshold current......Page 217
6.5 Justification for the two-dimensional approach......Page 221
6.6 Ambipolar materials and devices......Page 223
6.7 Contact effects and other simple nonidealities......Page 226
6.7.1 Insulator leakage......Page 230
6.7.2 Contact resistance......Page 232
6.7.3 Contact barriers......Page 236
6.7.4 Grain boundaries......Page 238
6.7.5 Parallel conductance......Page 243
6.8 Metallic contacts in TFTs......Page 244
6.9 Normally-on TFTs......Page 245
6.9.1 Narrow gap semiconductors......Page 251
6.9.2 Thick TFTs......Page 254
6.9.3 Doped semiconductors and inversion-channel TFT......Page 257
6.9.4 Metal–insulator–metal TFT......Page 259
6.10 Effects of traps......Page 261
6.10.1 Traps and threshold voltage......Page 263
6.10.2 Traps and output curves......Page 264
6.10.3 Traps and transfer curves......Page 265
6.10.4 Traps and ‘stressing’ (threshold-voltage shift)......Page 268
6.10.5 Traps and transients......Page 279
6.10.6 The origin of the traps......Page 282
6.10.7 Summary of the effects of traps on the TFT characteristics......Page 284
6.11 Admittance spectroscopy for the determination of the mobility in TFTs......Page 286
6.12 Summary of TFT measurements......Page 287
Appendix A Derivation of Equations (2.21), (2.25), (6.95) and (6.101)......Page 290
Bibliography......Page 296
Index......Page 300