research review
Debut for MBE-grown wurtzite AlGaN
UK researchers have found a novel method of producing AlxGa1-xN bulk crystals of designed composition for use in UV LED device manufacturing.
N-based UV LEDs are currently being investigated for applications in water purification, solid-state lighting and drug detection. However,it is difficult to produce devices with a high output, because material quality tends to be compromised by the significant differences in the lattice parameters of GaN and AlN and Alx
Alx Ga1-x Ga1-x N.
Now the University of Nottingham and the University of Strathclyde have grown, what they claim, are the first 2 inch diameter wurtzite Alx
Ga1-x N bulk crystals by plasma-
assisted molecular beam epitaxy (PA-MBE). The Nottingham group has recently used the PA-MBE technique for bulk crystal growth and has produced zinc-blende GaN layers of up to 100µm in thickness (see
www.compoundsemiconductor.net/csc/feat ures-details.php?cat=features &id=31168).
Furthermore, theyhave also demonstrated the scalability of the process by growing free-standing zinc-blendeGaN layers of up to 3 inches in diameter.
This new PA-MBE process for the growth of bulk zinc-blende layers has now produced free-standing wurtzite Alx wurtzite Alx
Ga1-x Ga1-x N wafers. Bulk N films were grown by MBE
on 2inch GaAs (111)B substrates with Al content (x) from 0 up to 0.5. Secondary ion mass spectroscopy data shows that the MBE method allows the growth of bulk Alx
Ga1-x N crystals with a constant
composition. EPMA data confirms a uniform lateral distribution of aluminium content across the diameter of the 2 inch wafer for wurtzite Alx
Ga1-x N bulk crystals. Sergei
Novikov, from Nottingham University says these results open the way for the potential MBE production of Alx
Ga1-x
of designed composition for UV LED devices.
For more details of the results published here, please see the paper “Wurtzite Alx
Ga1-x
beam epitaxy,” by S.V. Novikov et al, J. Crystal Growth (2011), doi:10.1016/j.jcrysgro.2011.03.016.
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54
www.compoundsemiconductor.net June 2011 N bulk crystals grown by molecular N bulk substrates
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