High Carrier Lifetime Bulk-Grown 4H-SiC Substrates for Power Applications

2006 ◽  
Vol 911 ◽  
Author(s):  
David Malta ◽  
J.R. Jenny ◽  
V.F. Tsvetkov ◽  
M. Das ◽  
St. G. Müller ◽  
...  
Keyword(s):  
Carrier Lifetime ◽  
Minority Carrier ◽  
Deep Level ◽  
Minority Carrier Lifetime ◽  
Drift Region ◽  
Disordered Lattice ◽  
High Temperature Anneal ◽  
Decay Times ◽  
Photoconductivity Decay ◽  
High Carrier

AbstractA thermal anneal process has been developed that significantly enhances minority carrier lifetime (MCL) in bulk-grown substrates. Microwave photoconductivity decay (MPCD) measurements on bulk grown substrates subjected to this process have exhibited decay times in excess of 35 μs. Electron Beam Induced Current (EBIC) measurements indicated a minority carrier diffusion length (MCDL) of 65 μm resulting in a calculated MCL of 15 μs, well within the range of that measured by MPCD. Deep level transient spectroscopic (DLTS) analysis of samples subjected to this anneal process indicated that a significant reduction of deep level defects, particularly Z1/2, may account for the significantly enhanced lifetimes. The enhanced lifetime is coincident with a transformation of the original as-grown crystal into a strained or disordered lattice configuration as a result of the high temperature anneal process. PiN diodes were fabricated employing 350 μm thick bulk-grown substrates as the intrinsic drift region and thin p- and n-type epitaxial layers on either face of the substrate to act as the anode and cathode, respectively. Conductivity modulation was achieved in these diodes with a 10x effective carrier concentration increase over the background doping as extracted from the differential on-resistance. Significant stacking fault generation observed during forward operation served as additional evidence of conductivity modulation and underscores the importance of reducing dislocation densities in substrates in order to produce a viable bulk-grown drift layer.

Influence of Epilayer Thickness and Structural Defects on the Minority Carrier Lifetime in 4H-SiC

2013 ◽  
Vol 740-742 ◽  
pp. 633-636 ◽  
Author(s):  
Birgit Kallinger ◽  
Patrick Berwian ◽  
Jochen Friedrich ◽  
Mathias Rommel ◽  
Maral Azizi ◽  
...  
Keyword(s):  
Carrier Lifetime ◽  
Minority Carrier ◽  
Deep Level ◽  
Surface Recombination ◽  
Minority Carrier Lifetime ◽  
Structural Defects ◽  
Effective Lifetime ◽  
Recombination Lifetime ◽  
Photoconductivity Decay ◽  
Transient Spectroscopy

4H-SiC homoepitaxial layers with different thicknesses from 12.5 µm up to 50 µm were investigated by microwave-detected photoconductivity decay (µ-PCD), deep level transient spectroscopy (DLTS) and defect selective etching (DSE) to shed light on the influence of the epilayer thickness and structural defects on the effective minority carrier lifetime. It is shown that the effective lifetime, resulting directly from the µ-PCD measurement, is significantly influenced by the surface recombination lifetime. Therefore, an adequate correction of the measured data is necessary to determine the bulk lifetime. The bulk lifetime of these epilayers is in the order of several microseconds. Furthermore, areas with high dislocation density are correlated to areas with locally reduced effective lifetime.

Improvement of Minority Carrier Lifetime in Thick 4H-SiC Epi-layers by Multiple Thermal Oxidations and Anneals

2013 ◽  
Vol 1538 ◽  
pp. 329-333 ◽  
Author(s):  
Lin Cheng ◽  
Michael J. O’Loughlin ◽  
Alexander V. Suvorov ◽  
Edward R. Van Brunt ◽  
Albert A. Burk ◽  
...  
Keyword(s):  
High Temperature ◽  
Carrier Lifetime ◽  
Minority Carrier ◽  
Minority Carrier Lifetime ◽  
Power Devices ◽  
Oxidation Treatment ◽  
Temperature Oxidation ◽  
Oxidation Step ◽  
High Temperature Anneal ◽  
Lifetime Enhancement

ABSTRACTThis paper details the development of a technique to improve the minority carrier lifetime of 4H-SiC thick (≥ 100 μm) n-type epitaxial layers through multiple thermal oxidations. A steady improvement in lifetime is seen with each oxidation step, improving from a starting ambipolar carrier lifetime of 1.09 µs to 11.2 µs after 4 oxidation steps and a high-temperature anneal. This multiple-oxidation lifetime enhancement technique is compared to a single high-temperature oxidation step, and a carbon implantation followed by a high-temperature anneal, which are traditional ways to achieve high ambipolar lifetime in 4H-SiC n-type epilayers. The multiple oxidation treatment resulted in a high minimum carrier lifetime of 6 µs, compared to < 2 µs for other treatments. The implications of lifetime enhancement to high-voltage/high-current 4H-SiC power devices are also discussed.

Minority Carrier Lifetime Measurements in Specific Epitaxial 4H-SiC Layers by the Microwave Photoconductivity Decay

2009 ◽  
Vol 615-617 ◽  
pp. 295-298 ◽  
Author(s):  
Laurent Ottaviani ◽  
Olivier Palais ◽  
Damien Barakel ◽  
Marcel Pasquinelli
Keyword(s):  
Absorption Spectra ◽  
Carrier Lifetime ◽  
Minority Carrier ◽  
Optical Excitation ◽  
Minority Carrier Lifetime ◽  
Lifetime Measurements ◽  
Recombination Processes ◽  
Photoconductivity Decay ◽  
P Type ◽  
Non Destructive

We report on measurements of the minority carrier lifetime for different epitaxial 4H-SiC layers by using the microwave photoconductivity decay (µ-PCD) method. This is a non-contacting, non-destructive method very useful for the monitoring of recombination processes in semiconductor material. Distinct samples have been analyzed, giving different lifetime values. Transmittance and absorption spectra have also been carried out. The n-type layers, giving rise to a specific absorption peak near 470 nm, are not sensitive to optical excitation for the used wavelengths, as opposite to p-type layers whose lifetime values depend on thickness and doping.

Understanding The Role Of Defects In Limiting The Minority Carrier Lifetime In Sic

1997 ◽  
Vol 483 ◽  
Author(s):  
W. A. Doolittle ◽  
A. Rohatgi ◽  
R. Ahrenkiel ◽  
D. Levi ◽  
G. Augustine ◽  
...  
Keyword(s):  
Electron Beam ◽  
Electrical Activity ◽  
Carrier Lifetime ◽  
Minority Carrier ◽  
Diffusion Length ◽  
Deep Level ◽  
Minority Carrier Lifetime ◽  
Injection Level ◽  
Growth Step ◽  
Sem Image

AbstractDeep level Transient Spectroscopy (DLTS), Electron Beam Induced Current (EBIC), EBIC Diffusion Length Mapping (EBIC-DLM) and contactless Photoconductive Decay (PCD) were used to characterize both bulk substrates and epitaxially grown Silicon Carbide films. Traps as deep as 0.93 eV were observed via DLTS. These traps may play a role in the persistent photoconductivity effect. EBIC reveals the electrical activity of the well known triangular defects. However, only some of these defects display electrical activity consistent with that of 3C-SiC inclusions, others do not. Additionally, not all defects identified in the EBIC images are observable in the topographic SEM image, possibly indicating a new, yet unidentified defect. EBIC revealed the electrical activity of defects including micro-pipes, dislocations (or possibly growth step edge decoration), surface polish damage, and bulk defects. Diffusion length maps of SiC indicate wide variations in diffusion length on both microscopic and macroscopic scales. EBIC-DLMindicatedepitaxial 4H SiC resulted in diffusion lengths from 0.1 to 3 μm, while bulk values were less than 0.07 μm. PCD measurements indicate tens of nanosecond to microsecond variations in lifetime. Lifetime verses injection level variations are observed and explained on the basis of trap energy. The injection level dependence of lifetime was observed at various nitrogen doping concentrations. Finally, electron beam annealing is found to dramatically improve the minority carrier lifetime in epitaxial SiC.

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