Barcelona, 31 May- 2 June Contacts to High-Resistivity Semiconductors Arie Ruzin School of EE, Faculty of Engineering, Tel Aviv University, Israel
Barcelona, 31 May- 2 June Outline Motivation Schottky and Ohmic contacts to Low- semiconductors Simulated results for Low- and High- semiconductors Injecting contacts to High- semiconductors Space Charge Limited Current Summary
Barcelona, 31 May- 2 June “Classic” Presentation for High- Energy Bands (??)
Barcelona, 31 May- 2 June Taking Into Account Majority Carriers Only (??) Majority Carriers only ?
Barcelona, 31 May- 2 June Thermionic Emission (??) Thermionic emission ?
Barcelona, 31 May- 2 June Thermionic emission ? Thermionic Emission (??), 1.5eV barriers (?)
Barcelona, 31 May- 2 June Textbook Contacts (Low- Semiconductor) EiEi SchottkyOhmicOhmic injecting? EFEF qBqB ECEC EVEV Metal Semiconductor qFqF qsqs EFEF EiEi ECEC EVEV qFqF EFEF EiEi ECEC EVEV qFqF qBqB
Barcelona, 31 May- 2 June Low- CdTe Diode (N D =10 15, B =1eV) (The diode is 1 mm long) Zoom on the front 10 m Zero Bias Low Bias Energy band structure
Barcelona, 31 May- 2 June Low- CdTe Diode (N D =10 15, B =1eV) (The diode is 1 mm long) Zoom on the front 10 m E -field profiles under bias
Barcelona, 31 May- 2 June Low- CdTe Diode (N D =10 15, B =1eV) Free carrier densities
Barcelona, 31 May- 2 June Low- CdTe Diode (N D =10 15, B =1eV) (The diode is 1 mm long) Current density Thermionic emission limited Bulk limited
Barcelona, 31 May- 2 June EFEF EiEi qBqB ECEC EVEV Metal Semiconductor qFqF qsqs EFEF EiEi ECEC EVEV qFqF qBqB EFEF EiEi ECEC EVEV qFqF High- Schottky Diode (?) SchottkyOhmicOhmic injecting?
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =1eV) Zero Bias Low Bias Energy band structure
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =1eV) Free carrier densities
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =1eV) Forward and Reverse Currents
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =1.3eV) Zero Bias Low Bias Energy band structure
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =1.3eV) Free Carrier Concentration
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =1.3eV) E -Field and Potential profiles
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =1.3eV) Band Structure under forward bias ECEC EVEV
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =1.3eV) Forward and Reverse Currents Mott’s Law fit:
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =1.3eV,SRH) With SRH Recombination Without SRH Recombination Free Carrier Concentration with and without SRH
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =1.3eV,SRH) Free Carrier Concentration with and without SRH With SRH Recombination Without SRH Recombination
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =1.3eV,SRH) Currents with and without SRH
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =0.2eV) Energy band structure ECEC EVEV
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =0.2eV) Free Carrier Concentration
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =0.2eV) E -Field and Potential profiles
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =0.2eV) Band Structure
Barcelona, 31 May- 2 June High- CdTe Diode (N D =10 6, B =0.2eV) Currents Mott’s Law fit:
Barcelona, 31 May- 2 June Conclusions Band bending in high- semiconductors is mainly attributed to free carrier charge – NOT dopant ions In high- semiconductors Schottky devices thermionic emission is not the dominant forward current mechanism In case on any band bending (positive or “ negative ” barrier) the “ bulk ” resistivity is strongly affected by free carrier injection In case of significant Schottky barrier the current transport is dominated by minority carriers Space Charge Limited Current may occur both, in Schottky and “ Ohmic ” contacts (except flat-band conditions)
Barcelona, 31 May- 2 June Thank you