See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/275350879 High-field Electrical Transport in Single Crystal CVD Diamond Diodes, Presentation Conference Paper · June 2006 CITATIONS READS 0 31 4 authors , including: Jan Isberg Markus Gabrysch Uppsala University Uppsala University 162 PUBLICATIONS 3,153 CITATIONS 39 PUBLICATIONS 323 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Laser Dump View project Wave power View project All content following this page was uploaded by Jan Isberg on 24 April 2015. The user has requested enhancement of the downloaded file.
High-field Electrical Transport in Single Crystal CVD Diamond Diodes Uppsala University: Jan Isberg Markus Gabrysch Element Six Ltd: Antonella Tajani Daniel Twitchen Jan Isberg, Markus Gabrysch Uppsala University Antonella Tajani, Daniel Twitchen Element Six Ltd
Contents • Impact Ionization at high electric fields • High voltage diamond diodes • Attempts to measure impact ionization coefficients in SC-CVD diamond • Summary
Impact Ionization Silicon Carbide E Impact Ionisation Diodes Experiment Summary Holes and electrons accelerated in high electric field attain enough energy to create new electron hole pairs by impact ionization R. Raghunathan, B. Baliga, Solid-State Electronics 43 (1999) 199-211
Modelling Impact Ionization = µ + ∇ j qn E qD n Drift-diffusion n n n = µ − ∇ currents j qp E qD p p p p ∂ n = ∇ ⋅ − + α + α | | | | q j r j j ∂ n SRH n n p p t Impact Continuity eq. including ∂ Ionisation avalanche generation p = ∇ ⋅ − + α + α | | | | q j r j j Diodes ∂ p SRH n n p p t Experiment q + − ∇ ⋅ = − + − Poisson eq. ( ) E p n N N ε Summary a d ∂ E = + + ε j j j Total current ∂ n p t − b α = n a e E n n Cynoweth relation b − α = p a e E p p
Avalanche Simulation Hole conc. 2kV over 50 µ m Impact Ionisation t=0 Diodes Experiment Summary α 7.2kV over 50 µ m
Avalanche simulation movies Impact Ionisation Diodes Experiment Summary
Charge multiplication Low voltage: no carrier multiplication, electrons extracted quickly, holes Impact extracted after transit Ionisation Diodes Experiment Summary High voltage: generation of electron-hole pairs by impact ionization
HV p-i-metal Diamond Diode Al or Au cathode Impact Ionisation intrinsic (< 10 13 [B]/cm 3 , very low [N]) few µ m Diodes Experiment p + (~ 10 20 [B]/cm 3 ) 50-500 µ m Summary anode Ti/Al/Au or p ++ boron ion-implanted Ti/Al/Pt/Au
Boron Doping In-growth B doping in the range 10 15 to 10 21 cm -3 • for thick layers • No contamination between doped and undoped layers • Sharp interfaces (<1 µm) Impact Ionisation Diodes i p Experiment p i Summary Optical micrograph SIMS analysis
HV p-i-metal diamond diodes Au cathode Space charge limited Similar to intrinsic hole current in vacuum p + intrinsic layer diode p ++ anode Impact Ionisation Diodes Edge field enhancement Experiment Summary
Forward Conduction Forward conduction: space charge limited hole current in Similar to intrinsic layer e - vacuum diode Impact Ionisation - + p+ i Diodes Experiment Summary Ideally: Mott – Gurney behaviour εµ 2 9 V = h j 3 8 L ε 3 / 2 L 8 q c.f. Child’s law for V = j vacuum tubes 2 9 L m (ballistic transport) e
Layer thickness C-V measurement on 1.2 mm 2 diode. Note almost constant Impact capacitance in this Ionisation type of diode Diodes Experiment Summary Diode illuminated from side, 10 μm i-layer
EBIC in diamond Impact Au Ionisation i Diodes p + Experiment Summary Ti/Al/Au no secondary impact ionization at attainable bias voltage…
Impact ionization experiment Impact Ionisation Diodes Experiment Summary Two α -emitting spherical gold tips made at The Svedberg Lab (3 & 5 kBq) Advantages: •Small contact area •Experiment can be done in insulating oil → higher bias possible
Alpha particle penetration Impact Ionisation 0° incidence Diodes Experiment Summary Isotropic distribution
Impact ionization setup Impact Ionisation Diodes Experiment Summary
Preliminary results Dashed line: a p = 6.0·10 5 cm -1 and b p =0.8·10 7 V/cm Solid line: a p = 4.0·10 6 cm -1 , b p =1.1·10 7 V/cm Impact Ionisation Diodes Experiment Summary Noise (shot noise) due to excessive leakage current
Summary • Measurements of impact ionization coefficients in diamond difficult due to Impact th very high electric fields necessary Ionisation Diodes • Carrier multiplication from impact Experiment Summary ionization at high electric fields has been observed • Reduced leakage currents necessary to obtain reliable data on avalanche ionization coefficients View publication stats View publication stats
Recommend
More recommend
