IBPOWER Kick off meeting – 07/02/08
Specific issues relating to plasma-MBE
Growth under group III-rich versus group V-rich conditions
Control of composition is different from conventional MBE growth
Strong polarisation fields for wurtzite nitrides
Controlled p-doping of InGaN
IBPOWER Kick off meeting – 07/02/08
GaN MBE growth kinetics
Heying et al, Appl Phys Lett 77 (2000) 2885
In would be similar, but at a lower temp.
IBPOWER Kick off meeting – 07/02/08
Growth under N-rich conditions
IBPOWER Kick off meeting – 07/02/08
Growth under optimum conditions
IBPOWER Kick off meeting – 07/02/08
Composition control
Conventional MBE:- fix In:Ga ratio and use excess group V flux
For plasma MBE under group III richconditions:- fix Ga:N ratio and useexcess In – excess In will re-evaporate
IBPOWER Kick off meeting – 07/02/08
Controlled doping of InGaN?
Recent evidence at ICNS7 for InN p-n junction
In may enhance Mg solubility in InGaN
Depth of Mg in InGaN may be < 200meV
Influence of inversion and accumulation layers at the surface Veal et al JCG 288 (2006) 268
For InN there is strong electron accumulation at the surface due to pinning of the Fermi energy high in the conduction band – This will be an issue for P-doping
IBPOWER Kick off meeting – 07/02/08
Polarisation fields
In GaN the polarisation fields enhance electron andhole mobility to the surface and substrate
In-rich InGaN will be very different due to the surface accumulation layer
IBPOWER Kick off meeting – 07/02/08
Proposed programme- questions?
What In content should we aim for initially? The calculations suggest the Mn level is optimum for 15% Ga is that correct?
What are the optimum thicknesses for the P-i-N layers?
Should the top contact be graded towards a higher band-gap to ensure photons are absorbed in the Mn doped InGaN region?
Choice of substrate – sapphire, GaAs or GaN templates?
Should we consider cubic InGaN as an alternative?
IBPOWER Kick off meeting – 07/02/08
Initial growth programme
Growth of InGaN with the correct In content and correct polarity using AlN buffer layers.
P & N-doping of InGaN with Mg and Si
Mn doping of InGaN
P-i-N structures with and without Mn
Initial layers available for etching studies by partners