1. Growth and impurity doping of compound semiconductor nanowires Solid State Physics, Lund University, Lund E. Norberg, P. Wickert, H. Nilsson, J. Trägårdh, P. Ramvall, G. Statkute, K. Dick, K. Deppert, L. Samuelson Philips Research laboratories, Eindhoven H -Y. Li, O. Wunnicke, G. Immink, M van Weert, M. A. Verheijen, L-F. Feiner, R. Algra, E. P. A. M. Bakkers 1. Introduction 2. Nanowire impurity doping 3. InP pn junctions M.T. Borgström magnus.borgstrom@ftf.lth.se

2. Energy (transformed from one form to another) 50 times increase in energy consumption since pre industrial era (15 terawatt- years per year) US, 300 million, 5 % of world population > 21 % world energy consumption India, 1000 million, 16 % worlds population 3.4 % world energy consumption Mrs Bulletin, 2008. 33

3. Energy availability

4. Power to the people (renewable energy) Mrs Bulletin, 2008. 33 Off-Grid solar cells: Nasa ISS

5. Metal particle liquid Au-III eutect vapor III-V nanowire time VLS (Vapor-Liquid-Solid) Crystal Growth Wagner and Ellis, APL, 1964 Small lateral dimensions: Elastic strain relaxation via surface Single nucleation event (III/V on Si) Nanowires

6. Impurity doping in nanowires Particle assisted growth: Low temperature (400-500ºC)MOVPE 600-700ºC Via catalyst particle ? Complex growth dynamics [111] growth direction crystal structure Large surface/bulk ratio: Surface states Characterisation: Chemically (EDX) Electrically (Field effect) Optically (PL) Atom probe

7. Deliberate NW doping in literature Hiruma (GaAs p-n junction, APL 1992) Meyyappan (p and n-type ZnO, Nano letters 2004) H-M. Kim (GaN p-n junction, Nano letters 2004) Appenzeller (Ge p-n junction, Nano letters 2006) Bakkers (p and n –type InP, InAs, Nano letters 2007) Lieber (p and n-type InP, GaN, Si p-n junction, dopant modulation) Lieber, Nano Letters 2008

8. Evaluate doping – nw-FET Drude model,   nq  Carrier concentration, n = doping concentration Mobility (µ) extracted from gate-sweep measurements Conductivity (σ) extracted from I-V n-type

9. TESn for n-doping (Sn:InP ionization energy 5.9 meV) Gate voltage dependent action - n-type transconductance + IV (ohmic contacts) threshold voltage (non ohmic contacts)

10. TESn for n-doping (Sn:InP ionization energy 5.9 meV) Gate voltage dependent action - n-type transconductance + IV (ohmic contacts) threshold voltage (non ohmic contacts) TESn: excellent n type InP dopant precursor

11. Dimethylzinc for p-doping (Zn:InP ionization energy 35 meV) DMZn enhances the nanowire growth rate and suppresses side wall growth Nucleation problems for high dopant precursor molar fraction X DMZn =1e-6, 20minX DMZn =1e-5, 20minX DMZn =5e-5, 20min

12. Evaluate doping – Results DMZn p -type PL behaviour P-type gate voltage dependent behaviour Normally turned off at zero gate voltage: low doping Incomplete DMZn pyrolysis Van Weert el al, APL, 2006

13. DiEthylZinc for p doping DEZn more effective dopant precursor than DMZn InP :DEZn V th =10V (~10 18 cm -3 ) Minot et al, Nano Letters, 2007

14. n + p junctions X TESn =1E-5, X DMZn =5.5 E-5 N D =6E18 cm-3, N A = xE17 80 nm Au catalyst order is important n- InP (111)B n-InP p-InP

15. n + p junction- IV pn junction behaviour Reverse breakdown voltage about 20V Ideality factor around 3 Do they shine?

16. Electroluminescence Light emitting diode Quantum efficiency ~10 -5 at 300K

17. Photo current measurements V oc (707 W/cm2) = 0.97V

18. Summary InP TESn – n type dopant with excellent controllability H2S – n type dopant (high doping levels shown) DMZn- affects nanowire growth rate - low doping levels DEZn – versatile p-dopant precursor InAs/InP Core-Shell modulation doping pn-junctions